Split up leak detector into two stages for better leak reporting.

content/shell/renderer/layout_test/leak_detector.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/shell/renderer/layout_test/leak_detector.h"
 
 #include "base/json/json_writer.h"
 #include "base/logging.h"
 #include "base/values.h"
 #include "content/shell/renderer/layout_test/blink_test_runner.h"
@@ skipping 42 matching lines @@
   previous_result_.numberOfLiveScriptPromises = kInitialNumberOfScriptPromises;
   previous_result_.numberOfLiveFrames = kInitialNumberOfLiveFrames;
   previous_result_.numberOfLiveV8PerContextData =
     kInitialNumberOfV8PerContextData;
 }
 
 LeakDetector::~LeakDetector() {
 }
 
 void LeakDetector::TryLeakDetection(blink::WebLocalFrame* frame) {
-  web_leak_detector_->collectGarbageAndGetDOMCounts(frame);
+  web_leak_detector_->prepareForLeakDetection(frame);
+  web_leak_detector_->collectGarbageAndReport();
 }
 
 void LeakDetector::onLeakDetectionComplete(
     const WebLeakDetectorClient::Result& result) {
   LeakDetectionResult report;
   report.leaked = false;
   base::DictionaryValue detail;
 
   if (previous_result_.numberOfLiveAudioNodes < result.numberOfLiveAudioNodes) {
     base::ListValue* list = new base::ListValue();
@@ skipping 59 matching lines @@
     base::JSONWriter::Write(detail, &detail_str);
     report.detail = detail_str;
     report.leaked = true;
   }
 
   previous_result_ = result;
   test_runner_->ReportLeakDetectionResult(report);
 }
 
 }  // namespace content