Remove the 2-level input method system & InputMethodBridge.

ui/views/controls/prefix_selector.cc

Index: ui/views/controls/prefix_selector.cc
diff --git a/ui/views/controls/prefix_selector.cc b/ui/views/controls/prefix_selector.cc
index f7e8f66fa833828cf983972e85d568a92445b2f4..c2384321b6f77d47e43f1d129407ba1d685418a3 100644
--- a/ui/views/controls/prefix_selector.cc
+++ b/ui/views/controls/prefix_selector.cc
@@ -55,10 +55,6 @@ void PrefixSelector::InsertChar(base::char16 ch, int flags) {
   OnTextInput(base::string16(1, ch));
 }
 
-gfx::NativeWindow PrefixSelector::GetAttachedWindow() const {
-  return prefix_delegate_->GetWidget()->GetNativeWindow();
-}
-
 ui::TextInputType PrefixSelector::GetTextInputType() const {
   return ui::TEXT_INPUT_TYPE_TEXT;
 }