Conservative update button/label/textfield content

ui/views/controls/textfield/textfield.cc

 // Copyright (c) 2012 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.
 
 #include "ui/views/controls/textfield/textfield.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/string_util.h"
@@ skipping 131 matching lines @@
 }
 
 void Textfield::SetTextInputType(ui::TextInputType type) {
   text_input_type_ = type;
   bool should_be_obscured = type == ui::TEXT_INPUT_TYPE_PASSWORD;
   if (IsObscured() != should_be_obscured)
     SetObscured(should_be_obscured);
 }
 
 void Textfield::SetText(const string16& text) {
+  if (text == text_)
+    return;
   text_ = text;
   if (native_wrapper_)
     native_wrapper_->UpdateText();
 }
 
 void Textfield::AppendText(const string16& text) {
   text_ += text;
   if (native_wrapper_)
     native_wrapper_->AppendText(text);
 }
@@ skipping 324 matching lines @@
 NativeTextfieldWrapper* NativeTextfieldWrapper::CreateWrapper(
     Textfield* field) {
 #if defined(OS_WIN) && !defined(USE_AURA)
   if (!UseNativeTextfieldViews())
     return new NativeTextfieldWin(field);
 #endif
   return new NativeTextfieldViews(field);
 }
 
 }  // namespace views