Allow XHR timeout attribute to be overridden after send(), per spec

Source/core/loader/WorkerThreadableLoader.h

Index: Source/core/loader/WorkerThreadableLoader.h
diff --git a/Source/core/loader/WorkerThreadableLoader.h b/Source/core/loader/WorkerThreadableLoader.h
index 2709b22aa184d0f34168ea74a27bcf2cd2b56bde..b3a09aff0796d7749c5806a0b465c29d3d5506f7 100644
--- a/Source/core/loader/WorkerThreadableLoader.h
+++ b/Source/core/loader/WorkerThreadableLoader.h
@@ -61,6 +61,8 @@ namespace blink {
 
         virtual ~WorkerThreadableLoader();
 
+        virtual void overrideTimeout(unsigned long timeout) OVERRIDE;
+
         virtual void cancel() OVERRIDE;
 
     private:
@@ -87,6 +89,7 @@ namespace blink {
         public:
             // All executed on the worker context's thread.
             MainThreadBridge(PassRefPtr<ThreadableLoaderClientWrapper>, PassOwnPtr<ThreadableLoaderClient>, WorkerLoaderProxy&, const ResourceRequest&, const ThreadableLoaderOptions&, const ResourceLoaderOptions&, const String& outgoingReferrer);
+            void overrideTimeout(unsigned long timeoutMilliseconds);
             void cancel();
             void destroy();
 
@@ -99,6 +102,7 @@ namespace blink {
             virtual ~MainThreadBridge();
 
             static void mainThreadCreateLoader(ExecutionContext*, MainThreadBridge*, PassOwnPtr<CrossThreadResourceRequestData>, ThreadableLoaderOptions, ResourceLoaderOptions, const String& outgoingReferrer);
+            static void mainThreadOverrideTimeout(ExecutionContext*, MainThreadBridge*, unsigned long timeoutMilliseconds);
             static void mainThreadCancel(ExecutionContext*, MainThreadBridge*);
             virtual void didSendData(unsigned long long bytesSent, unsigned long long totalBytesToBeSent) OVERRIDE;
             virtual void didReceiveResponse(unsigned long identifier, const ResourceResponse&) OVERRIDE;