Use base::string16 for CompositionText.Text instead of converting to utf-8 and back unnecessarily.

chromeos/ime/composition_text.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROMEOS_IME_COMPOSITION_TEXT_H_
 #define CHROMEOS_IME_COMPOSITION_TEXT_H_
 
 #include <string>
 #include <vector>
+
 #include "base/basictypes.h"
+#include "base/strings/string16.h"
 #include "chromeos/chromeos_export.h"
 
 namespace chromeos {
 
 class CHROMEOS_EXPORT CompositionText {
  public:
   enum UnderlineType {
     COMPOSITION_TEXT_UNDERLINE_SINGLE = 1,
     COMPOSITION_TEXT_UNDERLINE_DOUBLE = 2,
     COMPOSITION_TEXT_UNDERLINE_ERROR  = 4,
   };
 
   struct UnderlineAttribute {
     UnderlineType type;
     uint32 start_index;  // The inclusive start index.
     uint32 end_index;  // The exclusive end index.
   };
 
   CompositionText();
   virtual ~CompositionText();
 
   // Accessors
-  const std::string& text() const { return text_; }
-  void set_text(const std::string& text) { text_ = text; }
+  const base::string16& text() const { return text_; }
+  void set_text(const base::string16& text) { text_ = text; }
 
   const std::vector<UnderlineAttribute>& underline_attributes() const {
     return underline_attributes_;
   }
 
   std::vector<UnderlineAttribute>* mutable_underline_attributes() {
     return &underline_attributes_;
   }
 
   uint32 selection_start() const { return selection_start_; }
   void set_selection_start(uint32 selection_start) {
     selection_start_ = selection_start;
   }
 
   uint32 selection_end() const { return selection_end_; }
   void set_selection_end(uint32 selection_end) {
     selection_end_ = selection_end;
   }
 
   void CopyFrom(const CompositionText& obj);
 
  private:
-  std::string text_;
+  base::string16 text_;
   std::vector<UnderlineAttribute> underline_attributes_;
   uint32 selection_start_;
   uint32 selection_end_;
 
   DISALLOW_COPY_AND_ASSIGN(CompositionText);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_IME_COMPOSITION_TEXT_H_