Migrate CandidateWindow::Entry to string16.

ui/base/ime/chromeos/ime_bridge.h

Index: ui/base/ime/chromeos/ime_bridge.h
diff --git a/ui/base/ime/chromeos/ime_bridge.h b/ui/base/ime/chromeos/ime_bridge.h
index c7049db32b061f96ef27564f8b581f660d89a515..bf2866568fa25623bafdfe728a9ba4ce895c9ae1 100644
--- a/ui/base/ime/chromeos/ime_bridge.h
+++ b/ui/base/ime/chromeos/ime_bridge.h
@@ -8,6 +8,7 @@
 #include <string>
 #include "base/basictypes.h"
 #include "base/callback.h"
+#include "base/strings/string16.h"
 #include "ui/base/ime/text_input_mode.h"
 #include "ui/base/ime/text_input_type.h"
 #include "ui/base/ui_base_export.h"
@@ -112,8 +113,9 @@ class UI_BASE_EXPORT IBusPanelCandidateWindowHandlerInterface {
                                  bool visible) = 0;
 
   // Called when the IME updates the preedit text. The |text| is given in
-  // UTF-8 encoding.
-  virtual void UpdatePreeditText(const std::string& text, uint32 cursor_pos,
+  // UTF-16 encoding.
+  virtual void UpdatePreeditText(const base::string16& text,
+                                 uint32 cursor_pos,
                                  bool visible) = 0;
 
   // Called when the application changes its caret bounds.