Conservative update button/label/textfield content

ui/views/controls/textfield/textfield.cc

Index: ui/views/controls/textfield/textfield.cc
diff --git a/ui/views/controls/textfield/textfield.cc b/ui/views/controls/textfield/textfield.cc
index d4e9f604a302ec56048c5f65d9c35db64ebe6cb6..6711aedc5206770c86e5be0c09f3b2c9e07d7264 100644
--- a/ui/views/controls/textfield/textfield.cc
+++ b/ui/views/controls/textfield/textfield.cc
@@ -149,6 +149,8 @@ void Textfield::SetTextInputType(ui::TextInputType type) {
 }
 
 void Textfield::SetText(const string16& text) {
+  if (text == text_)
+    return;
   text_ = text;
   if (native_wrapper_)
     native_wrapper_->UpdateText();