Remove the 2-level input method system & InputMethodBridge.

ui/views/controls/combobox/combobox.h

Index: ui/views/controls/combobox/combobox.h
diff --git a/ui/views/controls/combobox/combobox.h b/ui/views/controls/combobox/combobox.h
index 4355504eb301d1d6b6f035b4fcd4b9202787a63e..55087645ba72ffa1e7671e8dd17721c4263e2c55 100644
--- a/ui/views/controls/combobox/combobox.h
+++ b/ui/views/controls/combobox/combobox.h
@@ -102,7 +102,6 @@ class VIEWS_EXPORT Combobox : public MenuDelegate,
   void OnFocus() override;
   void OnBlur() override;
   void GetAccessibleState(ui::AXViewState* state) override;
-  ui::TextInputClient* GetTextInputClient() override;
   void Layout() override;
 
   // Overridden from MenuDelegate:
@@ -164,6 +163,8 @@ class VIEWS_EXPORT Combobox : public MenuDelegate,
   // Handles the clicking event.
   void HandleClickEvent();
 
+  PrefixSelector* GetPrefixSelector();
+
   // Our model. Not owned.
   ui::ComboboxModel* model_;