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

third_party/WebKit/public/web/WebLeakDetector.h

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 35 matching lines @@
         unsigned numberOfLiveResources;
         unsigned numberOfLiveActiveDOMObjects;
         unsigned numberOfLiveScriptPromises;
         unsigned numberOfLiveFrames;
         unsigned numberOfLiveV8PerContextData;
     };
 
     virtual void onLeakDetectionComplete(const Result&) = 0;
 };
 
+// |WebLeakDetector| detects leaks of various Blink objects, counting
+// the ones remaining after having reset Blink's global state and
+// collected all garbage. See |WebLeakDetectorClient::Results|
+// for the kinds of objects supported.
 class WebLeakDetector {
 public:
     virtual ~WebLeakDetector() { }
 
     BLINK_EXPORT static WebLeakDetector* create(WebLeakDetectorClient*);
 
-    // Cleans up the DOM objects and counts them. |WebLeakDetectorClient::onLeakDetectionComplete()| is called when done.
-    // This is supposed to be used for detecting DOM-object leaks.
+    // Leak detection can either be performed in one go using
+    // |collectGarbageAndGetDOMCounts()| or in two separate
+    // stages (|prepareForLeakDetection()|, |collectGarbageAndReport()|).
+    //
+    // The latter option giving you the opportunity to perform
+    // additional releasing of resources in between the two
+    // stages, should you need it.
+
+    // The all-in-one-go option, performing the |prepareForLeakDetection()|
+    // and |collectGarbageAndReport()| stages in sequence.
     virtual void collectGarbageAndGetDOMCounts(WebLocalFrame*) = 0;

[haraken, 2015/11/25 08:16:30]

There is only one call site of collectGarbageAndGetDOMCounts. I'd remove the
collectGarbageAndGetDOMCounts and replace it with prepareForLeaDetection +
collectGarbageAndReport (to decrease the number of public APIs).

Then m_haveReported won't be needed.

[sof, 2015/11/25 08:40:21]

Done, retired collectGarbageAndGetDOMCounts() + synced surrounding comments.

+
+    // Perform initial stage of preparing for leak detection,
+    // releasing references to resources held globally.
+    virtual void prepareForLeakDetection(WebLocalFrame*) = 0;
+
+    // Garbage collect Blink's heaps and report leak counts.
+    // |WebLeakDetectorClient::onLeakDetectionComplete()| is called
+    // upon completion.
+    virtual void collectGarbageAndReport() = 0;
 };
 
 } // namespace blink
 
 #endif // WebLeakDetector_h