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..58db04190089067770846bc3cab700eedab189da
--- /dev/null
+++ b/ui/android/java/src/org/chromium/ui/base/EventHandler.java
@@ -0,0 +1,28 @@
+// 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.JNINamespace;
+
+/**
+ * Class used to forward view, input events down to native.
+ */
+@JNINamespace("ui")
+public class EventHandler {

[boliu, 2016/12/06 23:15:46]

should add a comment that the java object can only be used while the native
ViewAndroid is alive, which is a super hard guarantee to maintain without checks

I think ViewAndroid should hold a ref to this object, and clear the native
pointer in ViewAndroid destructor

then can assert in methods like onPhysicalBackingSizeChanged that the native
pointer is not cleared

[Jinsuk Kim, 2016/12/07 12:36:28]

Done.

+    private final long mNativeView;
+
+    public EventHandler(long nativeView) {
+        mNativeView = nativeView;
+        nativeSetEventHandler(mNativeView);
+    }
+
+    public void onPhysicalBackingSizeChanged(int width, int height) {
+        nativeOnPhysicalBackingSizeChanged(mNativeView, width, height);
+    }
+
+    private static native void nativeSetEventHandler(long viewAndroid);
+    private static native void nativeOnPhysicalBackingSizeChanged(long viewAndroid,
+            int width, int height);
+}