Remove dead code related to compositing from Sky

sky/viewer/platform/platform_impl.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 "sky/viewer/platform/platform_impl.h"
 
 #include <cmath>
 
 #include "base/debug/trace_event.h"
 #include "base/rand_util.h"
@@ skipping 92 matching lines @@
 }
 
 void PlatformImpl::stopSharedTimer() {
   shared_timer_.Stop();
 }
 
 base::SingleThreadTaskRunner* PlatformImpl::mainThreadTaskRunner() {
   return main_thread_task_runner_.get();
 }
 
-bool PlatformImpl::isThreadedCompositingEnabled() {
-  return true;
-}
-
 mojo::NetworkService* PlatformImpl::networkService() {
   return network_service_.get();
 }
 
 blink::WebURLLoader* PlatformImpl::createURLLoader() {
   return new WebURLLoaderImpl(network_service_.get());
 }
 
 blink::WebURLError PlatformImpl::cancelledError(const blink::WebURL& url)
     const {
@@ skipping 90 matching lines @@
     const unsigned char* category_group_enabled,
     const char* name,
     TraceEventHandle handle) {
   base::debug::TraceEventHandle traceEventHandle;
   memcpy(&traceEventHandle, &handle, sizeof(handle));
   TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
       category_group_enabled, name, traceEventHandle);
 }
 
 }  // namespace sky