Refactor ResourceHandler API.

content/browser/loader/resource_handler.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This is the browser side of the resource dispatcher, it receives requests
 // from the RenderProcessHosts, and dispatches them to URLRequests. It then
 // fowards the messages from the URLRequests back to the correct process for
 // handling.
 //
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
@@ skipping 20 matching lines @@
 
 namespace content {
 class ResourceController;
 class ResourceMessageFilter;
 class ResourceRequestInfoImpl;
 struct ResourceResponse;
 
 // The resource dispatcher host uses this interface to process network events
 // for an URLRequest instance.  A ResourceHandler's lifetime is bound to its
 // associated URLRequest.
+//
+// For all methods that take a bool |defer_or_cancel| pointer, the pointer has
+// an initial value of false.  It should be set to true if the request should be
+// deferred until a later point in time, at which point the ResourceContoller's
+// Resume() method may be called to continue the request, or its Cancel() method
+// to cancel the request.  It must also be set to true if the
+// ResourceController's method to cancel the request are called synchronously.
 class CONTENT_EXPORT ResourceHandler
     : public NON_EXPORTED_BASE(base::NonThreadSafe) {
  public:
   virtual ~ResourceHandler();
 
-  // Sets the controller for this handler.
+  // Sets the controller for this handler. The controller can be used to resume
+  // the request after deferring it, or to cancel the request.
+  //
+  // On cancel, teardown will start asynchronously.
   virtual void SetController(ResourceController* controller);
 
-  // The request was redirected to a new URL.  |*defer| has an initial value of
-  // false.  Set |*defer| to true to defer the redirect.  The redirect may be
-  // followed later on via ResourceDispatcherHost::FollowDeferredRedirect.  If
-  // the handler returns false, then the request is cancelled.
-  virtual bool OnRequestRedirected(const net::RedirectInfo& redirect_info,
+  // The request was redirected to a new URL.
+  virtual void OnRequestRedirected(const net::RedirectInfo& redirect_info,
                                    ResourceResponse* response,
-                                   bool* defer) = 0;
+                                   bool* defer_or_cancel) = 0;
 
-  // Response headers and meta data are available.  If the handler returns
-  // false, then the request is cancelled.  Set |*defer| to true to defer
-  // processing of the response.  Call ResourceDispatcherHostImpl::
-  // ResumeDeferredRequest to continue processing the response.
-  virtual bool OnResponseStarted(ResourceResponse* response, bool* defer) = 0;
+  // Response headers and meta data are available.
+  virtual void OnResponseStarted(ResourceResponse* response,
+                                 bool* defer_or_cancel) = 0;
 
   // Called before the net::URLRequest (whose url is |url|) is to be started.
-  // If the handler returns false, then the request is cancelled.  Otherwise if
-  // the return value is true, the ResourceHandler can delay the request from
-  // starting by setting |*defer = true|.  A deferred request will not have
-  // called net::URLRequest::Start(), and will not resume until someone calls
-  // ResourceDispatcherHost::StartDeferredRequest().
-  virtual bool OnWillStart(const GURL& url, bool* defer) = 0;
+  virtual void OnWillStart(const GURL& url, bool* defer_or_cancel) = 0;
 
   // Data will be read for the response.  Upon success, this method places the
   // size and address of the buffer where the data is to be written in its
   // out-params.  This call will be followed by either OnReadCompleted (on
   // successful read or EOF) or OnResponseCompleted (on error).  If
   // OnReadCompleted is called, the buffer may be recycled.  Otherwise, it may
   // not be recycled and may potentially outlive the handler.  If |min_size| is
   // not -1, it is the minimum size of the returned buffer.
   //
   // If the handler returns false, then the request is cancelled.  Otherwise,
-  // once data is available, OnReadCompleted will be called.
+  // once data is available, OnReadCompleted will be called.  The request must
+  // not be cancelled via the ResourceController during this call.
+  //
+  // TODO(mmenke): Make this work like other methods (Sync/async completion,
+  // cancel through the ResourceController).
   virtual bool OnWillRead(scoped_refptr<net::IOBuffer>* buf,
                           int* buf_size,
                           int min_size) = 0;
 
   // Data (*bytes_read bytes) was written into the buffer provided by
-  // OnWillRead.  A return value of false cancels the request, true continues
-  // reading data.  Set |*defer| to true to defer reading more response data.
-  // Call controller()->Resume() to continue reading response data.  A zero
-  // |bytes_read| signals that no further data is available.
-  virtual bool OnReadCompleted(int bytes_read, bool* defer) = 0;
+  // OnWillRead.  A zero |bytes_read| signals that no further data is available.
+  virtual void OnReadCompleted(int bytes_read, bool* defer_or_cancel) = 0;
 
   // The response is complete.  The final response status is given.  Set
-  // |*defer| to true to defer destruction to a later time.  Otherwise, the
-  // request will be destroyed upon return.
+  // |*defer| to true to defer destruction to a later time.  It will be
+  // completed by calling ResourceController::Resume().
+  // TODO(mmenke): Make cancellation do something reasonble during this call,
+  //   and document it here.
   virtual void OnResponseCompleted(const net::URLRequestStatus& status,
                                    bool* defer) = 0;
 
   // This notification is synthesized by the RedirectToFileResourceHandler
   // to indicate progress of 'download_to_file' requests. OnReadCompleted
   // calls are consumed by the RedirectToFileResourceHandler and replaced
   // with OnDataDownloaded calls.
   virtual void OnDataDownloaded(int bytes_downloaded) = 0;
 
  protected:
@@ skipping 10 matching lines @@
  private:
   ResourceController* controller_;
   net::URLRequest* request_;
 
   DISALLOW_COPY_AND_ASSIGN(ResourceHandler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_RESOURCE_HANDLER_H_