Remove the 2-level input method system & InputMethodBridge.

ui/aura/demo/demo_main.cc

Index: ui/aura/demo/demo_main.cc
diff --git a/ui/aura/demo/demo_main.cc b/ui/aura/demo/demo_main.cc
index 52a09d3d7b1fc45ffc8aed760a7ca329c0214fc0..5a06231f24527f04a1dac8e77d56138e20692899 100644
--- a/ui/aura/demo/demo_main.cc
+++ b/ui/aura/demo/demo_main.cc
@@ -49,7 +49,6 @@ class DemoWindowDelegate : public aura::WindowDelegate {
 
   void OnBoundsChanged(const gfx::Rect& old_bounds,
                        const gfx::Rect& new_bounds) override {}
-  ui::TextInputClient* GetFocusedTextInputClient() override { return nullptr; }
   gfx::NativeCursor GetCursor(const gfx::Point& point) override {
     return gfx::kNullCursor;
   }