CompositorWorkerProxyClientImpl to CompositorProxy cross thread reference is using WeakMember

third_party/WebKit/Source/web/CompositorMutatorImpl.h

Index: third_party/WebKit/Source/web/CompositorMutatorImpl.h
diff --git a/third_party/WebKit/Source/web/CompositorMutatorImpl.h b/third_party/WebKit/Source/web/CompositorMutatorImpl.h
index f8d13118a455df0b62bd72fc5d10d4d91329d6f2..14a6589fa1c915707355de568c1a55b2de4df396 100644
--- a/third_party/WebKit/Source/web/CompositorMutatorImpl.h
+++ b/third_party/WebKit/Source/web/CompositorMutatorImpl.h
@@ -23,6 +23,7 @@ class CompositorMutatorClient;
 // CompositorAnimators and sent to the compositor to generate a new compositor
 // frame.
 //
+// Owned by the main thread or control thread.

[flackr, 2017/04/04 02:17:07]

Unless I'm missing something, this should only be owned by the main thread if we
don't have a compositor thread, see:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/web/Compositor...

[keishi, 2017/04/04 05:18:32]

I'm unclear about when the compositor thread will be missing.

Should the comment here be "Owned by the control thread" because the only time
it is owned by the main thread is when we run with the
"--disable-compositor-thread" flag?

The only test where CompositorMutatorImpl is allocated on the main thread seems
to be "global-interface-listing-compositor-worker.html". Why doesn't it have a
compositor thread?

[keishi, 2017/04/04 05:54:43]

Done.

 // Should be accessed only on the compositor thread.
 class CompositorMutatorImpl final : public CompositorMutator {
   WTF_MAKE_NONCOPYABLE(CompositorMutatorImpl);