Turn off isLinkPreload() when used

third_party/WebKit/Source/core/fetch/Resource.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@kde.org>
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
     version 2 of the License, or (at your option) any later version.
@@ skipping 196 matching lines @@
 
     AtomicString httpContentType() const;
 
     bool wasCanceled() const { return m_error.isCancellation(); }
     bool errorOccurred() const { return m_status == LoadError || m_status == DecodeError; }
     bool loadFailedOrCanceled() { return !m_error.isNull(); }
 
     DataBufferingPolicy getDataBufferingPolicy() const { return m_options.dataBufferingPolicy; }
     void setDataBufferingPolicy(DataBufferingPolicy);
 
+    // The isPreloaded() flag is using a counter in order to make sure that even when
+    // multiple ResourceFetchers are preloading the resource, it will remain marked as
+    // preloaded until *all* of them have used it.
     bool isUnusedPreload() const { return isPreloaded() && getPreloadResult() == PreloadNotReferenced; }
     bool isPreloaded() const { return m_preloadCount; }
     void increasePreloadCount() { ++m_preloadCount; }
     void decreasePreloadCount() { ASSERT(m_preloadCount); --m_preloadCount; }
 
     bool canReuseRedirectChain();
     bool mustRevalidateDueToCacheHeaders();
     bool canUseCacheValidator();
     bool isCacheValidator() const { return m_isRevalidating; }
     bool hasCacheControlNoStoreHeader() const;
@@ skipping 19 matching lines @@
 
     virtual bool canReuse(const ResourceRequest&) const { return true; }
 
     // Used by the MemoryCache to reduce the memory consumption of the entry.
     void prune();
 
     virtual void onMemoryDump(WebMemoryDumpLevelOfDetail, WebProcessMemoryDump*) const;
 
     static const char* resourceTypeToString(Type, const FetchInitiatorInfo&);
 
+    void testOnlyWillAddClientOrObserver(PreloadReferencePolicy policy) { willAddClientOrObserver(policy); }

[Yoav Weiss, 2016/09/13 09:33:18]

Adding this test only method, since adding an actual observer (even a Mock one)
resulted in weird crashes around the m_observers HashCountedSet, which I suspect
is the result of it not being thread safe.

[Nate Chapin, 2016/09/13 22:34:17]

...this is all single threaded, isn't it? This explanation sounds suspect to me.
Are you sure the observer was getting both added and removed?

[Charlie Harrison, 2016/09/16 12:18:47]

I think a "ForTesting" suffix is more common and I think (?) it gets checked by
a presubmit that the method is only used for tests.

[Charlie Harrison, 2016/09/16 12:31:38]

Apologies this was a very out of date draft comment :)

+
 protected:
     Resource(const ResourceRequest&, Type, const ResourceLoaderOptions&);
 
     virtual void checkNotify();
 
     enum class MarkFinishedOption {
         ShouldMarkFinished,
         DoNotMarkFinished
     };
     void notifyClientsInternal(MarkFinishedOption);
@@ skipping 126 matching lines @@
 
     Resource::Type m_type;
 };
 
 #define DEFINE_RESOURCE_TYPE_CASTS(typeName) \
     DEFINE_TYPE_CASTS(typeName##Resource, Resource, resource, resource->getType() == Resource::typeName, resource.getType() == Resource::typeName);
 
 } // namespace blink
 
 #endif