Fetcher: Disable memory caching when Service Worker handles a request

Source/core/fetch/ResourceFetcher.cpp

Index: Source/core/fetch/ResourceFetcher.cpp
diff --git a/Source/core/fetch/ResourceFetcher.cpp b/Source/core/fetch/ResourceFetcher.cpp
index 240af5d6f13d2a0167cd8dd7c6fc9821acdab35f..42802199e5c8807187820a4024fffec54df53104 100644
--- a/Source/core/fetch/ResourceFetcher.cpp
+++ b/Source/core/fetch/ResourceFetcher.cpp
@@ -763,6 +763,17 @@ ResourcePtr<Resource> ResourceFetcher::requestResource(Resource::Type type, Fetc
         ASSERT(policy != Use || m_documentLoader->substituteData().isValid());
         ASSERT(policy != Revalidate);
         memoryCache()->remove(resource.get());
+    } else {
+        // Remove a resource to be handled by Service Worker from the cache to
+        // prevent reuse because Service Worker can serve an arbitrary resource
+        // for an URL and pollute a memory cache entry.
+        // FIXME: isControlledByServiceWorker() always returns false on main
+        // resource request, but main resource is always removed from the cache
+        // as the above comment (http://crbug.com/388375).
+        if (frame() && frame()->loader().client()->isControlledByServiceWorker()) {

[michaeln, 2014/10/09 00:35:26]

ouch, this is gonna hurt performance 

[nhiroki, 2014/10/09 02:34:15]

Yes, that's a sore point of this change. I'm going to make sure the performance
impact.

[dominicc (has gone to gerrit), 2014/10/09 02:45:24]

Actually... why don't we land this as-is and concurrently investigate
performance and alternatives? It represents forward progress. The change is
precise. Changing it or backing it out later won't be hard. This is less subtle
than what AppCache does.

All we need is a good regression test which will support future efforts.

+            ASSERT(policy == Load || policy == Reload);
+            memoryCache()->remove(resource.get());
+        }
     }
 
     requestLoadStarted(resource.get(), request, policy == Use ? ResourceLoadingFromCache : ResourceLoadingFromNetwork);
@@ -921,6 +932,11 @@ ResourceFetcher::RevalidationPolicy ResourceFetcher::determineRevalidationPolicy
     if (!existingResource)
         return Load;
 
+    // FIXME: Currently caching for a resource to be handled by Service Worker
+    // is disabled (http://crbug.com/388375).
+    if (frame() && frame()->loader().client()->isControlledByServiceWorker())
+        return Reload;
+
     // We already have a preload going for this URL.
     if (fetchRequest.forPreload() && existingResource->isPreloaded())
         return Use;