MemoryCache::resourceForURL(): add argument validation.

Source/core/fetch/MemoryCacheTest.cpp

 /*
  * Copyright (c) 2013, 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 536 matching lines @@
     ResourcePtr<FakeResource> resource2 = new FakeResource(ResourceRequest("http://test/resource"), Resource::Raw);
     resource2->setCacheIdentifier("foo");
     memoryCache()->add(resource2.get());
     EXPECT_TRUE(memoryCache()->contains(resource1.get()));
     EXPECT_TRUE(memoryCache()->contains(resource2.get()));
 
     const KURL url = KURL(ParsedURLString, "http://test/resource");
     EXPECT_EQ(resource1.get(), memoryCache()->resourceForURL(url));
     EXPECT_EQ(resource1.get(), memoryCache()->resourceForURL(url, memoryCache()->defaultCacheIdentifier()));
     EXPECT_EQ(resource2.get(), memoryCache()->resourceForURL(url, "foo"));
+    EXPECT_EQ(0, memoryCache()->resourceForURL(KURL()));
 
     ResourcePtr<FakeResource> resource3 = new FakeResource(ResourceRequest("http://test/resource"), Resource::Raw);
     resource3->setCacheIdentifier("foo");
     memoryCache()->remove(resource2.get());
     memoryCache()->add(resource3.get());
     EXPECT_TRUE(memoryCache()->contains(resource1.get()));
     EXPECT_FALSE(memoryCache()->contains(resource2.get()));
     EXPECT_TRUE(memoryCache()->contains(resource3.get()));
 
     ResourcePtr<FakeResource> resource4 = new FakeResource(ResourceRequest("http://test/resource"), Resource::Raw);
     resource4->setCacheIdentifier("foo");
     memoryCache()->replace(resource4.get(), resource3.get());
     EXPECT_TRUE(memoryCache()->contains(resource1.get()));
     EXPECT_FALSE(memoryCache()->contains(resource3.get()));
     EXPECT_TRUE(memoryCache()->contains(resource4.get()));
 
     WillBeHeapVector<RawPtrWillBeMember<Resource>> resources = memoryCache()->resourcesForURL(url);
     EXPECT_EQ(2u, resources.size());
 
     memoryCache()->evictResources();
     EXPECT_FALSE(memoryCache()->contains(resource1.get()));
     EXPECT_FALSE(memoryCache()->contains(resource3.get()));
 }
 
 } // namespace