Let IPC::SyncMessageFilter take advantage of thread-safe Send.

content/renderer/gpu/queue_message_swap_promise_unittest.cc

 // Copyright 2014 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 "content/renderer/gpu/queue_message_swap_promise.h"
 
 #include <vector>
 
 #include "base/memory/scoped_vector.h"
 #include "cc/output/swap_promise.h"
@@ skipping 13 matching lines @@
   using RenderWidget::QueueMessageImpl;
 
  private:
   ~TestRenderWidget() override {}
 
   DISALLOW_COPY_AND_ASSIGN(TestRenderWidget);
 };
 
 class TestSyncMessageFilter : public IPC::SyncMessageFilter {
  public:
-  TestSyncMessageFilter() : IPC::SyncMessageFilter(NULL) {}
+  TestSyncMessageFilter() : IPC::SyncMessageFilter(NULL, false) {}

[jam, 2015/08/04 23:06:41]

it would be nice to remove this one usage, so that we can hide
SyncMessageFilter's constructor and have the only way to get it be from
SyncChannel. That way we can ensure it's not created incorrectly.

can we do this by making QueueMessageSwapPromise take an IPC::Sender and not a
SyncMessageFilter? i looked through the calls to GetRenderWidget::QueueMessage,
which from cs looks like what's leading to the vectors of messages being put in
it. i only see two calls to it, both with async IPCs. so I don't even know why
SyncMessageFilter was used. also i believe this is only called on the main
thread? in which case it doesn't make sense to use SyncMessageFilter.

would be good to check with the gpu folks who added that method

 
   bool Send(IPC::Message* message) override {
     messages_.push_back(message);
     return true;
   }
 
   ScopedVector<IPC::Message>& messages() { return messages_; }
 
  private:
   ~TestSyncMessageFilter() override {}
@@ skipping 269 matching lines @@
 TEST_F(QueueMessageSwapPromiseTest, VisualStateSwapPromiseDidNotSwapSwapFails) {
   VisualStateSwapPromiseDidNotSwap(cc::SwapPromise::SWAP_FAILS);
 }
 
 TEST_F(QueueMessageSwapPromiseTest,
        VisualStateSwapPromiseDidNotSwapActivationFails) {
   VisualStateSwapPromiseDidNotSwap(cc::SwapPromise::ACTIVATION_FAILS);
 }
 
 }  // namespace content