Introduce ViewRoot to forward input/view events to native

ui/android/java/src/org/chromium/ui/base/WindowAndroid.java

Index: ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
diff --git a/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java b/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
index 2e2037f156d5d5b463f31646a0c2b6c0e0a6014d..d1970c26c01bad1703047b4d0a0a293568ccc0fd 100644
--- a/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
+++ b/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
@@ -110,6 +110,8 @@ public class WindowAndroid {
 
     private AndroidPermissionDelegate mPermissionDelegate;
 
+    private EventHandler mEventHandler;
+
     /**
      * An interface to notify listeners of changes in the soft keyboard's visibility.
      */
@@ -727,6 +729,16 @@ public class WindowAndroid {
         }
     }
 
+    /**
+     * @return {@link EventHandler} instance used to forward input/view events down to native.
+     */
+    public EventHandler getEventHandler() {
+        if (mEventHandler == null) {
+            mEventHandler = nativeGetEventHandlerForJava(mNativeWindowAndroid);
+        }
+        return mEventHandler;
+    }
+
     private native long nativeInit(int displayId);
     private native void nativeOnVSync(long nativeWindowAndroid,
                                       long vsyncTimeMicros,
@@ -735,5 +747,5 @@ public class WindowAndroid {
     private native void nativeOnActivityStopped(long nativeWindowAndroid);
     private native void nativeOnActivityStarted(long nativeWindowAndroid);
     private native void nativeDestroy(long nativeWindowAndroid);
-
+    private native EventHandler nativeGetEventHandlerForJava(long nativeWindowAndroid);
 }