CachedMetadata support for ServiceWorker script.

Source/core/workers/WorkerGlobalScope.h

 /*
  * Copyright (C) 2008, 2009 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 81 matching lines @@
     // WorkerGlobalScope
     WorkerGlobalScope* self() { return this; }
     WorkerConsole* console();
     WorkerLocation* location() const;
     void close();
 
     DEFINE_ATTRIBUTE_EVENT_LISTENER(error);
 
     // WorkerUtils
     virtual void importScripts(const Vector<String>& urls, ExceptionState&);
+    virtual void setCachedMetadata(const KURL&, const char* data, size_t size) { }
+    virtual void clearCachedMetadata(const KURL&) { }

[kinuko, 2015/02/16 14:18:38]

Hmm.  We modify all the WorkerThreadStartupData, WorkerGlobalScope and
WorkerThread to add cached metadata just for ServiceWorker (for now), which
feels a bit intrusive to me.

I think... we could probably introduce more specialized classes instead? 
Something like:

- Define WorkerScriptCachedMetadataClient as a supplement of WorkerClients,
which has setCachedMetadata(), clearCachedMetadata() and releaseCachedMetadata()
methods
- Implement ServiceWorkerScriptCachedMetadataClient, which holds cached
metadata, and has reference to WebServiceWorkerContextClient
- Instantiate ServiceWorkerScriptCachedMetadataClient in WebEmbeddedWorkerImpl
and provide it to worker
- In WorkerThread.cpp we create MetadataHandler with MetadataClient which can be
obtained via worker clients supplement interface

[horo, 2015/02/16 16:20:12]

I want to use WorkerScriptCachedMetadataHandler in
WorkerGlobalScope::importScripts() to support v8 cache for imported scripts in
future.

In this case, I think WorkerScriptCachedMetadataClient as a supplement of
WorkerClients is not suitable.

[kinuko, 2015/02/17 02:32:31]

How do you plan to get the cached metadata for importScripts?

[horo, 2015/02/17 03:32:18]

I will create WorkerScriptCachedMetadataHandler using scriptLoader's
cachedMetadata in the for loop of WorkerGlobalScope::importScripts() and pass it
to m_script->evaluate().

I created a WIP patch https://codereview.chromium.org/932773002

[kinuko, 2015/02/17 05:19:24]

Thanks. So having the client hold cached metadata is not good, I see. I still
feel it'd be a bit cleaner to have a dedicated client interface for handling
setCachedMetadata() / clearCachedMetadata() methods, but that might be an
overkill. Hmm. (I'm going to chat with you)

     WorkerNavigator* navigator() const;
 
     // ExecutionContextClient
     virtual WorkerEventQueue* eventQueue() const override final;
     virtual SecurityContext& securityContext() override final { return *this; }
 
     virtual bool isContextThread() const override final;
     virtual bool isJSExecutionForbidden() const override final;
 
     virtual double timerAlignmentInterval() const override final;
@@ skipping 67 matching lines @@
 
     unsigned long m_workerExceptionUniqueIdentifier;
     WillBeHeapHashMap<unsigned long, RefPtrWillBeMember<ConsoleMessage>> m_pendingMessages;
 };
 
 DEFINE_TYPE_CASTS(WorkerGlobalScope, ExecutionContext, context, context->isWorkerGlobalScope(), context.isWorkerGlobalScope());
 
 } // namespace blink
 
 #endif // WorkerGlobalScope_h