Introduce ViewRoot to forward input/view events to native

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

Index: ui/android/java/src/org/chromium/ui/base/EventHandler.java
diff --git a/ui/android/java/src/org/chromium/ui/base/EventHandler.java b/ui/android/java/src/org/chromium/ui/base/EventHandler.java
new file mode 100644
index 0000000000000000000000000000000000000000..0a6376cad768c3673fb8aba89a3472cdde1b45e8
--- /dev/null
+++ b/ui/android/java/src/org/chromium/ui/base/EventHandler.java
@@ -0,0 +1,35 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+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.
+ */
+@JNINamespace("ui")
+public class EventHandler {
+    // The corresponding native ViewAndroid. This object can only be used while
+    // the native instance is alive.
+    private long mNativeView;
+
+    public EventHandler(long nativeView) {

[boliu, 2016/12/08 05:01:06]

hide the constructor so that only ui code can create instances of this object,
ie imo android_webview code is doing an unnecessary layer violation

I'd prefer view_android create this from a static Create method.

[Jinsuk Kim, 2016/12/13 23:20:38]

Done.

+        mNativeView = nativeView;
+    }
+
+    public void onPhysicalBackingSizeChanged(int width, int height) {
+        assert mNativeView != 0;
+        nativeOnPhysicalBackingSizeChanged(mNativeView, width, height);
+    }
+
+    @CalledByNative
+    private void onDestroyNativeView() {
+        mNativeView = 0;
+    }
+
+    private static native void nativeOnPhysicalBackingSizeChanged(long viewAndroid,
+            int width, int height);
+}