Rewire Android WebView's compositor changed signal.

android_webview/browser/compositor_id.cc

Index: android_webview/browser/compositor_id.cc
diff --git a/android_webview/browser/compositor_id.cc b/android_webview/browser/compositor_id.cc
new file mode 100644
index 0000000000000000000000000000000000000000..65cdba0b305f38adb7cb91339ab09e76e29bfbd6
--- /dev/null
+++ b/android_webview/browser/compositor_id.cc
@@ -0,0 +1,25 @@
+// 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.
+
+#include "android_webview/browser/compositor_id.h"
+#include "content/public/common/child_process_host.h"
+
+namespace android_webview {
+
+CompositorID::CompositorID()
+    : process_id(content::ChildProcessHost::kInvalidUniqueID),
+      routing_id(content::ChildProcessHost::kInvalidUniqueID) {}
+
+CompositorID::CompositorID(int process_id, int routing_id)
+    : process_id(process_id), routing_id(routing_id) {}
+
+CompositorID::CompositorID(const CompositorID& other) = default;
+
+bool CompositorIDIsDifferent::operator()(const CompositorID& lhs,

[boliu, 2016/06/03 02:18:20]

need sorting, ie this should be <, not ==

[hush (inactive), 2016/06/09 22:44:52]

done

+                                         const CompositorID& rhs) const {
+  return (lhs.process_id != rhs.process_id) ||
+         (lhs.routing_id != rhs.routing_id);
+}
+
+}  // namespace android_webview