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

blimp/client/core/compositor/blimp_compositor_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.h"
 
+#include "base/message_loop/message_loop.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "blimp/client/core/compositor/blimp_compositor_dependencies.h"
 #include "blimp/client/core/compositor/blob_image_serialization_processor.h"
 #include "blimp/client/test/compositor/mock_compositor_dependencies.h"
 #include "cc/layers/layer.h"
 #include "cc/proto/compositor_message.pb.h"
 #include "cc/surfaces/surface_manager.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 89 matching lines @@
   EXPECT_CALL(compositor_client_,
               MockableSendWebGestureEvent(render_widget_id_))
       .Times(1);
 
   compositor_->SendProto(cc::proto::CompositorMessage());
   compositor_->SendGestureEvent(blink::WebGestureEvent());
 }
 
 }  // namespace client
 }  // namespace blimp