Introduce ViewRoot to forward input/view events to native

ui/android/window_android.h

Index: ui/android/window_android.h
diff --git a/ui/android/window_android.h b/ui/android/window_android.h
index 05279ced4c92a2a9e8827b15c67e0c94187a9e11..2ca1bf4409a7cc45ef8fc94d44edddf849b174db 100644
--- a/ui/android/window_android.h
+++ b/ui/android/window_android.h
@@ -74,6 +74,8 @@ class UI_ANDROID_EXPORT WindowAndroid : public ViewAndroid {
                          const base::android::JavaParamRef<jobject>& obj);
   void OnActivityStarted(JNIEnv* env,
                          const base::android::JavaParamRef<jobject>& obj);
+  base::android::ScopedJavaLocalRef<jobject> GetEventHandler(JNIEnv* env,

[boliu, 2016/12/14 01:26:42]

nit: this is function overloading, which is banned, even if it's accidental..
call this something else? GetOrCreateEventHandler? GetEventHandlerForJava?

[Jinsuk Kim, 2016/12/14 01:35:56]

Done. Chose the latter.

+      const base::android::JavaParamRef<jobject>& obj);
 
   // Return whether the specified Android permission is granted.
   bool HasPermission(const std::string& permission);
@@ -89,6 +91,7 @@ class UI_ANDROID_EXPORT WindowAndroid : public ViewAndroid {
   ~WindowAndroid() override;
 
   // ViewAndroid overrides.
+  using ViewAndroid::GetEventHandler;

[boliu, 2016/12/14 01:26:42]

this should not be required I think? a function that can't be resolved in the
child class should automatically call the parent one?

[Jinsuk Kim, 2016/12/14 01:35:56]

GetEventHandler above was hiding the overloaded one in the parent. Now that it
was renamed, this is not necessary any more. Removed.

http://stackoverflow.com/questions/15556535/calling-base-classs-overloaded-me...

   WindowAndroid* GetWindowAndroid() const override;
 
   // The ID of the display that this window belongs to.