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 8de53059160fd0e7cf8cb2198f29297b80c8bb0f..a58d4e3819ecf82bf45a6d62c936a9f4f387ce1a 100644
--- a/Source/core/fetch/Resource.cpp
+++ b/Source/core/fetch/Resource.cpp
@@ -364,6 +364,11 @@ bool Resource::unlock()
     return true;
 }
 
+bool Resource::hasRightHandleCountApartFromCache(unsigned targetCount) const
+{
+    return m_handleCount == targetCount + memoryCache()->contains(this);
+}
+
 void Resource::responseReceived(const ResourceResponse& response)
 {
     setResponse(response);
@@ -403,6 +408,17 @@ 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() const
+{
+    return !hasClients() && !m_loader && !m_preloadCount && hasRightHandleCountApartFromCache(0)
+        && !m_protectorCount && !m_resourceToRevalidate && !m_proxyResource;
+}
+
+bool Resource::hasOneHandleApartFromCache() const
+{
+    return hasRightHandleCountApartFromCache(1);
+}
+
 CachedMetadata* Resource::cachedMetadata(unsigned dataTypeID) const
 {
     if (!m_cachedMetadata || m_cachedMetadata->dataTypeID() != dataTypeID)
@@ -771,6 +787,8 @@ void Resource::unregisterHandle(ResourcePtrBase* h)
         unlock();
     } else if (m_handleCount == 1 && memoryCache()->contains(this)) {
         unlock();
+        if (!hasClients())
+            memoryCache()->prune(this);
     }
 }