Inform disk cache of WebKit memory cache hits.

content/common/view_messages.h

Index: content/common/view_messages.h
diff --git a/content/common/view_messages.h b/content/common/view_messages.h
index 0e04b5091b42de942406bad8781e4be154b49666..1093a373fddbe1dbf6377cd6700e5b9d30bab94b 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -1413,6 +1413,12 @@ IPC_MESSAGE_ROUTED2(ViewHostMsg_DidLoadResourceFromMemoryCache,
                     GURL /* url */,
                     std::string  /* security info */)
 
+// Sent when the renderer accesses a resource in its memory cache. Used to
+// synchronize the disk cache with the memory cache.
+IPC_MESSAGE_CONTROL2(ViewHostMsg_DidAccessResourceInMemoryCache,

[darin (slow to review), 2011/07/30 05:09:32]

it slightly bugs me that we have DidLoadResourceFromMemoryCache and
DidAccessResourceInMemoryCache.  those sound like synonyms, and it seems odd
that we should need to inform the browser twice about the same event.

i understand that you are doing this because one is a routed message and the
other is a control message.  one is handled on the UI thread of the browser and
the other is handled on the IO thread of the browser.

unfortunately, we do not have good infrastructure for intercepting a message
bound for the browser's UI thread, inspecting the message, and then letting the
message proceed on to the UI thread.  we have IPC MessageFilter which can be
used to intercept the IPCs on the IO thread, but that terminates the handling of
the IPC.

ideally, just piggy back on ViewHostMsg_DidLoadResourceFromMemoryCache for this
feature.  in the IO thread, we'd intercept the IPC, act on it, and then let the
IPC continue on to the UI thread.

maybe this is something to explore in the future?  but maybe there is an easy
way to do this now?

edit: jam points out that MessageFilter::OnMessageReceived can return false to
allow the message to be normally processed!

+                     GURL /* url */,
+                     std::string /* http method */)
+
 // Sent when the renderer displays insecure content in a secure page.
 IPC_MESSAGE_ROUTED0(ViewHostMsg_DidDisplayInsecureContent)