Makes delay commitText/setComposition can deal with empty text/composition.

chrome/browser/ui/input_method/input_method_engine.cc

Index: chrome/browser/ui/input_method/input_method_engine.cc
diff --git a/chrome/browser/ui/input_method/input_method_engine.cc b/chrome/browser/ui/input_method/input_method_engine.cc
index a2395de71d6149818400c830b1fb58c3a99d1049..ebdc95ffc5aa5d40538f96351fdf7ae8a08ae60e 100644
--- a/chrome/browser/ui/input_method/input_method_engine.cc
+++ b/chrome/browser/ui/input_method/input_method_engine.cc
@@ -146,8 +146,9 @@ void InputMethodEngine::UpdateComposition(
   ui::IMEInputContextHandlerInterface* input_context =
       ui::IMEBridge::Get()->GetInputContextHandler();
   // If the IME extension is handling key event, hold the composition text
-  // until the key event is handled.
-  if (input_context && !handling_key_event_) {
+  // until the key event is handled. However, if trying to clear the
+  // composition, do UpdateCompositionText at once.
+  if ((input_context && !handling_key_event_) || composition_.text.empty()) {
     input_context->UpdateCompositionText(composition_, cursor_pos, is_visible);

[Azure Wei, 2016/11/23 07:53:42]

In UpdateCompositionText(), we would send a faked key event:
https://cs.chromium.org/chromium/src/ui/base/ime/input_method_base.cc?q=Updat...
Not sure if this is a safe when handing key event.

[Shu Chen, 2016/11/24 02:57:57]

Done.

     composition_.Clear();
   }