diff --git a/src/base/clock_mock.h b/src/base/clock_mock.h
index ff1af9f..5639fa6 100644
--- a/src/base/clock_mock.h
+++ b/src/base/clock_mock.h
@@ -32,6 +32,7 @@
 
 #include <ctime>
 
+#include "base/port.h"
 #include "base/util.h"
 
 namespace mozc {
diff --git a/src/base/cpu_stats.h b/src/base/cpu_stats.h
index 575e276..c298e6c 100644
--- a/src/base/cpu_stats.h
+++ b/src/base/cpu_stats.h
@@ -39,12 +39,12 @@
   CPUStatsInterface() {}
   virtual ~CPUStatsInterface() {}
 
-  // returns the percentage of total CPU load since the last time
+  // Returns the percentage of total CPU load since the last time
   // this method was called.
   // The return value must be in the range of [0.0 .. 1.0].
   virtual float GetSystemCPULoad() = 0;
 
-  // returns the percentage of current process's CPU load
+  // Returns the percentage of current process's CPU load
   // since the last time this method was called.
   // If the process has multi-threads, the return value
   // may be larger than 1.0.
@@ -59,6 +59,9 @@
 // default implementation
 class CPUStats : public CPUStatsInterface {
  public:
+  CPUStats();
+  virtual ~CPUStats();
+
   // return 0.0 if CPU load is unknown
   float GetSystemCPULoad();
 
@@ -68,15 +71,13 @@
   // return the number of processors
   size_t GetNumberOfProcessors() const;
 
-  CPUStats();
-  virtual ~CPUStats();
-
  private:
   uint64 prev_system_total_times_;
   uint64 prev_system_cpu_times_;
   uint64 prev_current_process_total_times_;
   uint64 prev_current_process_cpu_times_;
 };
+
 }  // namespace mozc
 
 #endif  // MOZC_BASE_CPU_STATS_H_
diff --git a/src/base/init_test.cc b/src/base/init_test.cc
index 0e9096f..f95c10e 100644
--- a/src/base/init_test.cc
+++ b/src/base/init_test.cc
@@ -29,8 +29,6 @@
 
 #include "base/init.h"
 
-#include <string.h>
-#include "base/util.h"
 #include "testing/base/public/gunit.h"
 
 namespace mozc {
@@ -57,6 +55,5 @@
   EXPECT_EQ(4, g_counter);
 }
 
-
 }  // namespace
 }  // namespace mozc
diff --git a/src/base/multifile.h b/src/base/multifile.h
index 9b0fede..8dc5a12 100644
--- a/src/base/multifile.h
+++ b/src/base/multifile.h
@@ -33,7 +33,6 @@
 #ifndef MOZC_BASE_MULTIFILE_H_
 #define MOZC_BASE_MULTIFILE_H_
 
-#include <fstream>
 #include <string>
 #include <vector>
 
diff --git a/src/base/process.cc b/src/base/process.cc
index 898c340..7fb0ce3 100644
--- a/src/base/process.cc
+++ b/src/base/process.cc
@@ -37,7 +37,7 @@
 #include <string.h>
 #include <sys/stat.h>
 #include <cerrno>
-#endif  // WINDOWS
+#endif  // OS_WIN
 
 #ifdef OS_MACOSX
 #include <fcntl.h>
@@ -51,7 +51,7 @@
 #include <signal.h>
 #include <spawn.h>  // for posix_spawn().
 #include <sys/types.h>
-#endif
+#endif  // OS_LINUX
 
 #include <cstdlib>
 #include <vector>
diff --git a/src/base/process.h b/src/base/process.h
index b92374a..61106e3 100644
--- a/src/base/process.h
+++ b/src/base/process.h
@@ -32,14 +32,17 @@
 
 #include <string>
 
+#include "base/port.h"
+
 namespace mozc {
+
 class Process {
  public:
-  // Open the URL with the default browser.  If this function is not
+  // Opens the URL with the default browser.  If this function is not
   // supported on the OS or failed, false is returned.
   static bool OpenBrowser(const string &url);
 
-  // Spawn a process specified by path using arg as options.
+  // Spawns a process specified by path using arg as options.
   // On Windows Vista the process is spawned as the same level as the parent
   // process.
   // Return true if process is successfully launched.
@@ -50,18 +53,18 @@
   // specifies an directory ending with ".app", an application is
   // spawned in the OSX way.
   static bool SpawnProcess(
-      const string &path, const string& arg, size_t *pid = NULL);
+      const string &path, const string& arg, size_t *pid = nullptr);
 
   // A SpawnProcess wrapper to run an executable which is installed in
   // the Mozc server directory.
   static bool SpawnMozcProcess(
-      const string &filename, const string &arg, size_t *pid = NULL);
+      const string &filename, const string &arg, size_t *pid = nullptr);
 
-  // Wait process |pid| until it terminates.
-  // you can set timeout. if timeout is negative, wait forever.
+  // Waits for process |pid| to terminate up to |timeout|.
+  // If |timeout| is negative, waits forever.
   static bool WaitProcess(size_t pid, int timeout);
 
-  // return true if a process having |pid| is still alive.
+  // Returns true if a process having |pid| is still alive.
   // if the the current thread has no permission to get the status or
   // operation failed in system call, it returns |default_result|.
   // TODO(all):
@@ -71,7 +74,7 @@
   // creation time if this kind of false-positive matters.
   static bool IsProcessAlive(size_t pid, bool default_result);
 
-  // return true if a thread having |thread_id| is still alive.
+  // Returns true if a thread having |thread_id| is still alive.
   // if the current thread has no permission to get the status or
   // operation failed in system call, it returns |default_result|.
   // On Posix, it always returns |default_result| as thread_id is not supported.
@@ -82,13 +85,13 @@
   // creation time if this kind of false-positive matters.
   static bool IsThreadAlive(size_t thread_id, bool default_result);
 
-  // launch error message dialog
+  // Launches an error message dialog.
   static bool LaunchErrorMessageDialog(const string &type);
 
  private:
-  Process() {}
-  virtual ~Process() {}
+  DISALLOW_IMPLICIT_CONSTRUCTORS(Process);
 };
+
 }  // namespace mozc
 
 #endif  // MOZC_BASE_PROCESS_H_
diff --git a/src/base/process_mutex_test.cc b/src/base/process_mutex_test.cc
index 50e2a22..2abcb55 100644
--- a/src/base/process_mutex_test.cc
+++ b/src/base/process_mutex_test.cc
@@ -27,6 +27,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+#include "base/process_mutex.h"
+
 #ifndef OS_WIN
 #include <unistd.h>
 #include <cstdlib>
@@ -34,7 +36,6 @@
 
 #include "base/file_util.h"
 #include "base/logging.h"
-#include "base/process_mutex.h"
 #include "base/system_util.h"
 #include "base/util.h"
 #include "testing/base/public/gunit.h"
diff --git a/src/base/stopwatch.h b/src/base/stopwatch.h
index e527514..a2c77d8 100644
--- a/src/base/stopwatch.h
+++ b/src/base/stopwatch.h
@@ -33,6 +33,7 @@
 #include "base/port.h"
 
 namespace mozc {
+
 class Stopwatch {
  public:
   enum StopwatchState {
diff --git a/src/base/stopwatch_test.cc b/src/base/stopwatch_test.cc
index 420d7aa..8259135 100644
--- a/src/base/stopwatch_test.cc
+++ b/src/base/stopwatch_test.cc
@@ -29,12 +29,12 @@
 
 #include <numeric>
 
-#include "testing/base/public/googletest.h"
-#include "testing/base/public/gunit.h"
 #include "base/clock_mock.h"
 #include "base/scoped_ptr.h"
 #include "base/stopwatch.h"
 #include "base/util.h"
+#include "testing/base/public/googletest.h"
+#include "testing/base/public/gunit.h"
 
 namespace mozc {
 
diff --git a/src/base/text_converter_compiler.cc b/src/base/text_converter_compiler.cc
index 292ac2d..5a72e0a 100644
--- a/src/base/text_converter_compiler.cc
+++ b/src/base/text_converter_compiler.cc
@@ -31,6 +31,7 @@
 #include <vector>
 
 #include "base/file_stream.h"
+#include "base/flags.h"
 #include "base/logging.h"
 #include "base/text_converter.h"
 #include "base/util.h"
diff --git a/src/base/unnamed_event_test.cc b/src/base/unnamed_event_test.cc
index 8ac8824..c79fd5c 100644
--- a/src/base/unnamed_event_test.cc
+++ b/src/base/unnamed_event_test.cc
@@ -35,31 +35,31 @@
 #include "base/util.h"
 #include "testing/base/public/gunit.h"
 
+namespace mozc {
 namespace {
-class UnnamedEventNotifierThread: public mozc::Thread {
+
+class UnnamedEventNotifierThread : public Thread {
  public:
-  UnnamedEventNotifierThread(mozc::UnnamedEvent *event,
-                             int timeout)
+  UnnamedEventNotifierThread(UnnamedEvent *event, int timeout)
       : event_(event), timeout_(timeout) {}
 
  public:
-  void Run() {
-    mozc::Util::Sleep(timeout_);
+  virtual void Run() {
+    Util::Sleep(timeout_);
     LOG(INFO) << "Notify event";
     event_->Notify();
   }
 
  private:
-  mozc::UnnamedEvent *event_;
+  UnnamedEvent *event_;
   int timeout_;
 
   DISALLOW_COPY_AND_ASSIGN(UnnamedEventNotifierThread);
 };
-}  // namespace
 
 TEST(UnnamedEventTest, UnnamedEventTest) {
   {
-    mozc::UnnamedEvent event;
+    UnnamedEvent event;
     EXPECT_TRUE(event.IsAvailable());
     UnnamedEventNotifierThread t(&event, 400);
     t.Start();
@@ -70,7 +70,7 @@
   }
 
   {
-    mozc::UnnamedEvent event;
+    UnnamedEvent event;
     EXPECT_TRUE(event.IsAvailable());
     UnnamedEventNotifierThread t(&event, 100);
     t.Start();
@@ -79,7 +79,7 @@
   }
 
   {
-    mozc::UnnamedEvent event;
+    UnnamedEvent event;
     EXPECT_TRUE(event.IsAvailable());
     UnnamedEventNotifierThread t(&event, 3000);
     t.Start();
@@ -90,7 +90,7 @@
   }
 
   {
-    mozc::UnnamedEvent event;
+    UnnamedEvent event;
     EXPECT_TRUE(event.IsAvailable());
     UnnamedEventNotifierThread t(&event, 2000);
     t.Start();
@@ -102,15 +102,18 @@
 }
 
 TEST(UnnamedEventTest, NotifyBeforeWait) {
-  mozc::UnnamedEvent event;
+  UnnamedEvent event;
   ASSERT_TRUE(event.Notify());
   EXPECT_TRUE(event.Wait(100));
 }
 
 TEST(UnnamedEventTest, DoubleNotifyBeforeWait) {
-  mozc::UnnamedEvent event;
+  UnnamedEvent event;
   ASSERT_TRUE(event.Notify());
   ASSERT_TRUE(event.Notify());
   EXPECT_TRUE(event.Wait(100));
   EXPECT_FALSE(event.Wait(100));
 }
+
+}  // namespace
+}  // namespace mozc
diff --git a/src/base/url.h b/src/base/url.h
index 008ab8a..6cbaaaa 100644
--- a/src/base/url.h
+++ b/src/base/url.h
@@ -32,20 +32,22 @@
 
 #include <string>
 
+#include "base/port.h"
+
 namespace mozc {
-// util class to get URLs
+
 class URL {
  public:
-  // composes a URL for an uninstallation survey.
-  // note that we should set version
-  // because in Mac OS, we can not get mozc version from uninstaller binary.
+  // Composes a URL for an uninstallation survey.  Note that we should set
+  // version because, in Mac OS, we can not get mozc version from uninstaller
+  // binary.
   static bool GetUninstallationSurveyURL(const string &version, string *url);
 
   // should never be allocated.
  private:
-  URL();
-  virtual ~URL();
+  DISALLOW_IMPLICIT_CONSTRUCTORS(URL);
 };
+
 }  // namespace mozc
 
 #endif  // MOZC_BASE_URL_H_
diff --git a/src/base/url_test.cc b/src/base/url_test.cc
index 6fc7281..666330d 100644
--- a/src/base/url_test.cc
+++ b/src/base/url_test.cc
@@ -33,11 +33,11 @@
 #include <vector>
 
 #include "base/util.h"
-#include "base/version.h"
 #include "testing/base/public/gunit.h"
 
 namespace mozc {
 namespace {
+
 const char kSurveyBaseURL[] =
     "http://www.google.com/support/ime/japanese/bin/request.py";
 
@@ -53,7 +53,6 @@
   }
   return false;
 }
-}  // namespace
 
 TEST(URLTest, UninstallationSurveyURL) {
   string url;
@@ -85,4 +84,6 @@
   EXPECT_TRUE(FindEncodedParam(params, "hl", "jp"));
   EXPECT_TRUE(FindEncodedParam(params, "format", "inproduct"));
 }
+
+}  // namespace
 }  // namespace mozc
diff --git a/src/dictionary/file/dictionary_file_builder.cc b/src/dictionary/file/dictionary_file_builder.cc
index a8f2681..da3b56e 100644
--- a/src/dictionary/file/dictionary_file_builder.cc
+++ b/src/dictionary/file/dictionary_file_builder.cc
@@ -69,10 +69,8 @@
   ifs.read(ptr, len);
 
   sections_.push_back(DictionaryFileSection(ptr, len, ""));
-
   sections_.back().name =
       DictionaryFileCodecFactory::GetCodec()->GetSectionName(section_name);
-
   return true;
 }
 
diff --git a/src/dictionary/system/system_dictionary.cc b/src/dictionary/system/system_dictionary.cc
index 35d7f2e..85de1f0 100644
--- a/src/dictionary/system/system_dictionary.cc
+++ b/src/dictionary/system/system_dictionary.cc
@@ -263,7 +263,8 @@
     }
 
     if (token_info_.accent_encoding_type == TokenInfo::EMBEDDED_IN_TOKEN) {
-      token_.value += "_" + Util::StringPrintf("%d", token_info_.accent_type);
+      token_.value.append(1, '_')
+                  .append(Util::StringPrintf("%d", token_info_.accent_type));
     }
 
     if (token_info_.pos_type == TokenInfo::FREQUENT_POS) {
diff --git a/src/gui/character_pad/character_palette.cc b/src/gui/character_pad/character_palette.cc
index 6695f30..c879164 100644
--- a/src/gui/character_pad/character_palette.cc
+++ b/src/gui/character_pad/character_palette.cc
@@ -48,7 +48,6 @@
 
 namespace mozc {
 namespace gui {
-
 namespace {
 
 const char32 kHexBase = 16;
@@ -114,14 +113,15 @@
   { NULL, 0 }
 };
 
-// add child QTreeWidgetItem with the text "name" to parent.
-// return child item.
+// Adds a child QTreeWidgetItem with the text "name" to parent.
+// Returns the added child item.
 QTreeWidgetItem *AddItem(QTreeWidgetItem *parent, const char *name) {
   QTreeWidgetItem *item = new QTreeWidgetItem(parent);
   item->setText(0, QString::fromUtf8(name));
   parent->addChild(item);
   return item;
 }
+
 }  // namespace
 
 CharacterPalette::CharacterPalette(QWidget *parent)
@@ -485,5 +485,6 @@
   return QWidget::winEvent(message, result);
 }
 #endif  // OS_WIN
+
 }  // namespace gui
 }  // namespace mozc
diff --git a/src/gui/character_pad/windows_selection_handler.cc b/src/gui/character_pad/windows_selection_handler.cc
index 126e1fc..c4f4c86 100644
--- a/src/gui/character_pad/windows_selection_handler.cc
+++ b/src/gui/character_pad/windows_selection_handler.cc
@@ -28,13 +28,14 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #ifdef OS_WIN
+
 #include "gui/character_pad/windows_selection_handler.h"
 
 #include <windows.h>
 #include <QtCore/QString>
 #include <vector>
+
 #include "base/logging.h"
-#include "base/util.h"
 
 namespace mozc {
 namespace gui {
@@ -74,6 +75,8 @@
     return;
   }
 }
+
 }  // namespace gui
 }  // namespace mozc
+
 #endif   // OS_WIN
diff --git a/src/gui/character_pad/windows_selection_handler.h b/src/gui/character_pad/windows_selection_handler.h
index 5391899..e946029 100644
--- a/src/gui/character_pad/windows_selection_handler.h
+++ b/src/gui/character_pad/windows_selection_handler.h
@@ -29,11 +29,10 @@
 
 #ifndef MOZC_GUI_CHARACTER_PAD_WINDOWS_SELECTION_HANDLER_H_
 #define MOZC_GUI_CHARACTER_PAD_WINDOWS_SELECTION_HANDLER_H_
-
-#include <string>
-
 #ifdef OS_WIN
+
 #include <QtCore/QString>
+
 #include "gui/character_pad/selection_handler.h"
 
 namespace mozc {
@@ -41,11 +40,14 @@
 
 class WindowsSelectionHandler : public SelectionCallbackInterface {
  public:
-  virtual void Select(const QString &str);
   WindowsSelectionHandler();
   virtual ~WindowsSelectionHandler();
+
+  virtual void Select(const QString &str);
 };
-}
-}
-#endif
+
+}  // namespace gui
+}  // namespace mozc
+
+#endif  // OS_WIN
 #endif  // MOZC_GUI_CHARACTER_PAD_WINDOWS_SELECTION_HANDLER_H_
diff --git a/src/gui/config_dialog/combobox_delegate.cc b/src/gui/config_dialog/combobox_delegate.cc
index 51a46c8..ca73385 100644
--- a/src/gui/config_dialog/combobox_delegate.cc
+++ b/src/gui/config_dialog/combobox_delegate.cc
@@ -28,6 +28,7 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "gui/config_dialog/combobox_delegate.h"
+
 #include <QtGui/QtGui>
 #include <QtGui/QComboBox>
 
@@ -60,8 +61,7 @@
     QWidget *editor,
     const QModelIndex &index) const {
   QString str = index.model()->data(index, Qt::EditRole).toString();
-  QComboBox *comboBox =
-      static_cast<QComboBox*>(editor);
+  QComboBox *comboBox = static_cast<QComboBox*>(editor);
   if (comboBox == NULL) {
     return;
   }
@@ -71,8 +71,7 @@
 void ComboBoxDelegate::setModelData(
     QWidget *editor, QAbstractItemModel *model,
     const QModelIndex &index) const {
-  QComboBox *comboBox =
-      static_cast<QComboBox*>(editor);
+  QComboBox *comboBox = static_cast<QComboBox*>(editor);
   if (comboBox == NULL || model == NULL) {
     return;
   }
@@ -94,5 +93,6 @@
   emit commitData(editor);
   emit closeEditor(editor);
 }
-}  // gui
-}  // mozc
+
+}  // namespace gui
+}  // namespace mozc
diff --git a/src/gui/config_dialog/combobox_delegate.h b/src/gui/config_dialog/combobox_delegate.h
index e0bd1f5..39314a7 100644
--- a/src/gui/config_dialog/combobox_delegate.h
+++ b/src/gui/config_dialog/combobox_delegate.h
@@ -69,6 +69,8 @@
  private:
   QStringList item_list_;
 };
-}  // gui
-}  // mozc
+
+}  // namespace gui
+}  // namespace mozc
+
 #endif  // MOZC_GUI_CONFIG_DIALOG_COMBOBOX_DELEGATE_H_
diff --git a/src/mozc_version_template.txt b/src/mozc_version_template.txt
index 4bcf8bf..24e7bdf 100644
--- a/src/mozc_version_template.txt
+++ b/src/mozc_version_template.txt
@@ -1,6 +1,6 @@
 MAJOR=2
 MINOR=17
-BUILD=2090
+BUILD=2091
 REVISION=102
 # NACL_DICTIONARY_VERSION is the target version of the system dictionary to be
 # downloaded by NaCl Mozc.
diff --git a/src/prediction/predictor.cc b/src/prediction/predictor.cc
index 18d2807..1e816d3 100644
--- a/src/prediction/predictor.cc
+++ b/src/prediction/predictor.cc
@@ -47,6 +47,7 @@
 
 namespace mozc {
 namespace {
+
 const int kPredictionSize = 100;
 // On Mobile mode PREDICTION (including PARTIAL_PREDICTION) behaves like as
 // conversion so very large limit is preferable.
@@ -263,4 +264,5 @@
 
   return result;
 }
+
 }  // namespace mozc