Introduce ViewRoot forwarding input/view events to native

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

Index: ui/android/java/src/org/chromium/ui/base/ViewRoot.java
diff --git a/ui/android/java/src/org/chromium/ui/base/ViewRoot.java b/ui/android/java/src/org/chromium/ui/base/ViewRoot.java
index c224e8e3ed8c9cdfd31b3ed2e783e090ea42a4e7..4141c15a88356ee682812edd8c4bc00ca04e9ab8 100644
--- a/ui/android/java/src/org/chromium/ui/base/ViewRoot.java
+++ b/ui/android/java/src/org/chromium/ui/base/ViewRoot.java
@@ -4,29 +4,32 @@
 
 package org.chromium.ui.base;
 
-import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.JNINamespace;
 
 /**
  * Class used to forward view, input events down to native.
- *
- * TODO(jinsukkim): Add its native counterpart inheriting from ViewAndroid
- *     so that it will act as a root of ViewAndroid tree. It effectively
- *     replaces WindowAndroid in terms of the role.
  */
 @JNINamespace("ui")
 public class ViewRoot {
-    // The corresponding native ViewAndroid. This object can only be used while
+
+    private final WindowAndroid mWindowAndroid;
+
+    // The corresponding native instance. This class can only be used while
     // the native instance is alive.
     private long mNativeView;
 
-    @CalledByNative
-    private static ViewRoot create(long nativeView) {
-        return new ViewRoot(nativeView);
+    public static ViewRoot create(WindowAndroid window) {
+        if (window == null) throw new IllegalArgumentException("WindowAndroid should not be null");
+        return new ViewRoot(window);
+    }
+
+    private ViewRoot(WindowAndroid window) {
+        mNativeView = nativeInit(window.getNativePointer());
+        mWindowAndroid = window;
     }
 
-    private ViewRoot(long nativeView) {
-        mNativeView = nativeView;
+    public WindowAndroid getWindowAndroid() {
+        return mWindowAndroid;
     }
 
     /**
@@ -40,11 +43,18 @@ public class ViewRoot {
         nativeOnPhysicalBackingSizeChanged(mNativeView, width, height);
     }
 
-    @CalledByNative
-    private void onDestroyNativeView() {
+    public long getNativePtr() {
+        return mNativeView;
+    }
+
+    public void destroy() {
+        assert mNativeView != 0;
+        nativeDestroy(mNativeView);
         mNativeView = 0;
     }
 
-    private static native void nativeOnPhysicalBackingSizeChanged(long viewAndroid,
+    private native long nativeInit(long windowNativePointer);
+    private native void nativeDestroy(long nativeViewRoot);
+    private native void nativeOnPhysicalBackingSizeChanged(long nativeViewRoot,
             int width, int height);
 }