Remove unused thread.h include in trace_event_impl.h and fix IWUU.

blimp/client/core/compositor/blimp_compositor_frame_sink_unittest.cc

 // 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 "blimp/client/core/compositor/blimp_compositor_frame_sink.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/run_loop.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/threading/thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/test/fake_compositor_frame_sink_client.h"
 #include "cc/test/test_context_provider.h"
 #include "cc/test/test_context_support.h"
 #include "cc/test/test_gles2_interface.h"
 #include "cc/test/test_web_graphics_context_3d.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace blimp {
@@ skipping 188 matching lines @@
   // the main thread complete.
   base::RunLoop().RunUntilIdle();
   EXPECT_EQ(3, main_thread_proxy_->swap_count());
 
   EndTest();
 }
 
 }  // namespace
 }  // namespace client
 }  // namespace blimp