predictors: Add trace events to the resource_prefetch_predictor.

chrome/browser/predictors/resource_prefetcher.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 "chrome/browser/predictors/resource_prefetcher.h"
 
 #include <iterator>
 #include <utility>
 
+#include "base/trace_event/trace_event.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/base/io_buffer.h"
 #include "net/base/load_flags.h"
 #include "net/base/request_priority.h"
 #include "net/url_request/url_request_context.h"
 #include "url/origin.h"
 
 namespace {
 
 // The size of the buffer used to read the resource.
@@ skipping 13 matching lines @@
       config_(config),
       main_frame_url_(main_frame_url) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
 
   std::copy(urls.begin(), urls.end(), std::back_inserter(request_queue_));
 }
 
 ResourcePrefetcher::~ResourcePrefetcher() {}
 
 void ResourcePrefetcher::Start() {
+  TRACE_EVENT_ASYNC_BEGIN0("browser", "ResourcePrefetcher::Prefetch", this);
   DCHECK(thread_checker_.CalledOnValidThread());
 
   CHECK_EQ(state_, INITIALIZED);
   state_ = RUNNING;
 
   TryToLaunchPrefetchRequests();
 }
 
 void ResourcePrefetcher::Stop() {
+  TRACE_EVENT_ASYNC_END0("browser", "ResourcePrefetcher::Prefetch", this);
   DCHECK(thread_checker_.CalledOnValidThread());
 
   if (state_ == FINISHED)
     return;
 
   state_ = STOPPED;
 }
 
 void ResourcePrefetcher::TryToLaunchPrefetchRequests() {
   CHECK(state_ == RUNNING || state_ == STOPPED);
@@ skipping 135 matching lines @@
   if (bytes_read <= 0) {
     FinishRequest(request);
     return;
   }
 
   if (bytes_read > 0)
     ReadFullResponse(request);
 }
 
 }  // namespace predictors