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..823186d048573b65bbb3ce06b1528be98d2ae3eb
--- /dev/null
+++ b/android_webview/browser/compositor_id.cc
@@ -0,0 +1,38 @@
+// 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 CompositorID::operator==(const CompositorID& other) const {
+  return process_id == other.process_id && routing_id == other.routing_id;
+}
+
+bool CompositorID::operator<(const CompositorID& other) const {

[boliu, 2016/06/10 15:55:38]

Actually, overloading operator< was bad advice. Style guide says:

https://google.github.io/styleguide/cppguide.html#Operator_Overloading
For example, if you overload <, overload all the comparison operators, and make
sure < and > never return true for the same arguments.

There are still <= and >=, which are not used, but required by style guide.

So external "LessThan" might be better in this case

[hush (inactive), 2016/06/10 23:28:43]

i overloaded everything in the new patchset

+  if (process_id == other.process_id) {
+    return routing_id < other.routing_id;
+  }
+  return process_id < other.process_id;
+}
+
+bool CompositorID::operator>(const CompositorID& other) const {
+  return other < *this;
+}
+
+bool CompositorID::operator!=(const CompositorID& other) const {
+  return !(operator==(other));
+}
+
+}  // namespace android_webview