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..7b199fb65b1f5fdac45fe8f462ad48e4e4e32b6a
--- /dev/null
+++ b/android_webview/browser/compositor_id.cc
@@ -0,0 +1,37 @@
+// 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;
+
+CompositorID& CompositorID::operator=(const CompositorID& other) {
+  process_id = other.process_id;
+  routing_id = other.routing_id;
+  return *this;
+}
+
+bool CompositorID::Equals(const CompositorID& other) const {
+  return process_id == other.process_id && routing_id == other.routing_id;
+}
+
+bool CompositorIDComparator::operator()(const CompositorID& a,
+                                        const CompositorID& b) const {
+  if (a.process_id == b.process_id) {
+    return a.routing_id < b.routing_id;
+  }
+  return a.process_id < b.process_id;
+}
+
+}  // namespace android_webview