MemoryCache: make sure that Resources are evicted only when they can be deleted

Source/core/fetch/Resource.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@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
@@ skipping 346 matching lines @@
     if (!m_data->isLocked())
         return true;
 
     if (!memoryCache()->contains(this) || hasClients() || m_handleCount > 1 || m_proxyResource || m_resourceToRevalidate || !m_loadFinishTime || !isSafeToUnlock())
         return false;
 
     m_data->unlock();
     return true;
 }
 
+bool Resource::hasRightHandleCountApartFromCache(unsigned targetCount)
+{
+    bool inCache = memoryCache()->contains(this);
+    return (inCache && m_handleCount == targetCount + 1) || (!inCache && m_handleCount == targetCount);

[Philippe, 2014/03/26 16:04:07]

Nit: not sure this is more readable but in case you think it is, you can replace
this I believe with:

return m_handleCount == targetCount + !!memoryCache()->contains(this);

[Philippe, 2014/03/26 17:08:33]

You might not even need the '!!' though. We usually use this pattern to convert
pointers to integers but contains() already returns a bool here.

[clamy, 2014/03/27 10:47:16]

Done.

+}
+
 void Resource::responseReceived(const ResourceResponse& response)
 {
     setResponse(response);
     m_responseTimestamp = currentTime();
     String encoding = response.textEncodingName();
     if (!encoding.isNull())
         setEncoding(encoding);
 
     if (!m_resourceToRevalidate)
         return;
@@ skipping 19 matching lines @@
     // Currently, only one type of cached metadata per resource is supported.
     // If the need arises for multiple types of metadata per resource this could
     // be enhanced to store types of metadata in a map.
     ASSERT(!m_cachedMetadata);
 
     m_cachedMetadata = CachedMetadata::create(dataTypeID, data, size);
     const Vector<char>& serializedData = m_cachedMetadata->serialize();
     blink::Platform::current()->cacheMetadata(m_response.url(), m_response.responseTime(), serializedData.data(), serializedData.size());
 }
 
+bool Resource::canDelete()
+{
+    return !hasClients() && !m_loader && !m_preloadCount && hasRightHandleCountApartFromCache(0)
+        && !m_protectorCount && !m_resourceToRevalidate && !m_proxyResource;
+}
+
+bool Resource::hasOneHandleApartFromCache()
+{
+    return hasRightHandleCountApartFromCache(1);
+}
+
 CachedMetadata* Resource::cachedMetadata(unsigned dataTypeID) const
 {
     if (!m_cachedMetadata || m_cachedMetadata->dataTypeID() != dataTypeID)
         return 0;
     return m_cachedMetadata.get();
 }
 
 void Resource::setCacheLiveResourcePriority(CacheLiveResourcePriority priority)
 {
     if (memoryCache()->contains(this) && memoryCache()->isInLiveDecodedResourcesList(this) && cacheLiveResourcePriority() != static_cast<unsigned>(priority)) {
@@ skipping 348 matching lines @@
 
     if (m_resourceToRevalidate)
         m_handlesToRevalidate.remove(h);
 
     if (!m_handleCount) {
         if (deleteIfPossible())
             return;
         unlock();
     } else if (m_handleCount == 1 && memoryCache()->contains(this)) {
         unlock();
+        if (!hasClients())

[Philippe, 2014/03/26 16:04:07]

Nit: Do we still need this change?

[clamy, 2014/03/27 10:47:16]

Yes this is what is making it work with the rebase.

+            memoryCache()->prune(this);
     }
 }
 
 bool Resource::canReuseRedirectChain() const
 {
     for (size_t i = 0; i < m_redirectChain.size(); ++i) {
         if (!canUseResponse(m_redirectChain[i].m_redirectResponse, m_responseTimestamp))
             return false;
     }
     return true;
@@ skipping 190 matching lines @@
         return "Shader";
     case Resource::ImportResource:
         return "ImportResource";
     }
     ASSERT_NOT_REACHED();
     return "Unknown";
 }
 #endif // !LOG_DISABLED
 
 }