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

Source/core/fetch/Resource.cpp

Index: Source/core/fetch/Resource.cpp
diff --git a/Source/core/fetch/Resource.cpp b/Source/core/fetch/Resource.cpp
index fcbb7ce19a58503553f48890fe1d515554b2bdd0..e60ee341f51838a6314a8c22b4348ae09a831b84 100644
--- a/Source/core/fetch/Resource.cpp
+++ b/Source/core/fetch/Resource.cpp
@@ -364,6 +364,12 @@ bool Resource::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);
@@ -403,6 +409,17 @@ void Resource::setCachedMetadata(unsigned dataTypeID, const char* data, size_t s
     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)
@@ -771,6 +788,8 @@ void Resource::unregisterHandle(ResourcePtrBase* h)
         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);
     }
 }