Move MimeTypeResourceHandler before ThrottlingResourceHandler

content/browser/loader/intercepting_resource_handler.h

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Copyright 2016 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.
 
-#ifndef CONTENT_BROWSER_LOADER_MIME_TYPE_RESOURCE_HANDLER_H_
-#define CONTENT_BROWSER_LOADER_MIME_TYPE_RESOURCE_HANDLER_H_
+#ifndef CONTENT_BROWSER_LOADER_INTERCEPTING_RESOURCE_HANDLER_H_
+#define CONTENT_BROWSER_LOADER_INTERCEPTING_RESOURCE_HANDLER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "content/browser/loader/layered_resource_handler.h"
 #include "content/common/content_export.h"
-#include "content/public/browser/resource_controller.h"
 
 namespace net {
 class URLRequest;
 }
 
 namespace content {
 class PluginService;
 class ResourceDispatcherHostImpl;
 struct WebPluginInfo;
 
-// ResourceHandler that, if necessary, buffers a response body without passing
-// it to the next ResourceHandler until it can perform mime sniffing on it.
-// Once a response's MIME type is known, initiates special handling of the
-// response if needed (starts downloads, sends data to some plugin types via a
-// special channel).
-//
-// Uses the buffer provided by the original event handler for buffering, and
-// continues to reuses it until it can determine the MIME type
-// subsequent reads until it's done buffering.  As a result, the buffer
-// returned by the next ResourceHandler must have a capacity of at least
-// net::kMaxBytesToSniff * 2.
-//
-// Before a request is sent, this ResourceHandler will also set an appropriate
-// Accept header on the request based on its ResourceType, if one isn't already
-// present.
-class CONTENT_EXPORT MimeTypeResourceHandler
-    : public LayeredResourceHandler,
-      public ResourceController {
+// ResourceHandler that initiates special handling of the response if needed,
+// based on the response's MIME type (starts downloads, sends data to some
+// plugin types via a special channel).
+class CONTENT_EXPORT InterceptingResourceHandler
+    : public LayeredResourceHandler {
  public:
   // If ENABLE_PLUGINS is defined, |plugin_service| must not be NULL.
-  MimeTypeResourceHandler(std::unique_ptr<ResourceHandler> next_handler,
-                          ResourceDispatcherHostImpl* host,
-                          PluginService* plugin_service,
-                          net::URLRequest* request);
-  ~MimeTypeResourceHandler() override;
+  InterceptingResourceHandler(std::unique_ptr<ResourceHandler> next_handler,
+                              ResourceDispatcherHostImpl* host,
+                              PluginService* plugin_service,
+                              net::URLRequest* request);
+  ~InterceptingResourceHandler() override;
 
  private:
+  enum class State {
+    // In this state, the InterceptingResourceHandler is waiting for the mime
+    // type of the response to be identified, to check if the next handler
+    // should be replaced with an appropriate one.
+    STARTING,
+
+    // In this state, the InterceptingResourceHandler is waiting for the plugin
+    // info to be ready in order to possibly intercept the resource has a
+    // stream.
+    WAITING_FOR_PLUGINS,
+
+    // In this state, the InterceptingResourceHandler is waiting to copy the
+    // read buffer to the next handler if it was replaced. This is needed
+    // because MimeTypeResourceHandler may call OnWillRead before calling
+    // OnResponseStarted, that is before the InterceptingResourceHandler
+    // replaces the original ResourceHandler of the request. Therefore, the
+    // data read at that time should be copied to the new ResourceHandler.
+    WAITING_FOR_BUFFER_COPY,
+
+    // In this state, the InterceptingResourceHandler has replaced its next
+    // ResourceHandler if needed, and has ensured the buffered read data was
+    // properly transmitted to the new ResourceHandler. The
+    // InterceptingResourceHandler now acts as a pass-through ResourceHandler.
+    DONE,
+  };
+
   // ResourceHandler implementation:
-  void SetController(ResourceController* controller) override;
   bool OnResponseStarted(ResourceResponse* response, bool* defer) override;
-  bool OnWillStart(const GURL&, bool* defer) override;
   bool OnWillRead(scoped_refptr<net::IOBuffer>* buf,
                   int* buf_size,
                   int min_size) override;
   bool OnReadCompleted(int bytes_read, bool* defer) override;
-  void OnResponseCompleted(const net::URLRequestStatus& status,
-                           const std::string& security_info,
-                           bool* defer) override;
 
-  // ResourceController implementation:
-  void Resume() override;
-  void Cancel() override;
-  void CancelAndIgnore() override;
-  void CancelWithError(int error_code) override;
+  bool MakeHandlerChoice(bool* defer);
 
-  bool ProcessResponse(bool* defer);
-
-  bool ShouldSniffContent();
-  bool DetermineMimeType();
   // Determines whether a plugin will handle the current request, and if so,
   // sets up the handler to direct the response to that plugin. Returns false
   // if there is an error and the request should be cancelled and true
   // otherwise. |defer| is set to true if plugin data is stale and needs to be
   // refreshed before the request can be handled (in this case the function
   // still returns true). If the request is directed to a plugin,
   // |handled_by_plugin| is set to true.
   bool SelectPluginHandler(bool* defer, bool* handled_by_plugin);
   // Returns false if the request should be cancelled.
   bool SelectNextHandler(bool* defer);
   bool UseAlternateNextHandler(std::unique_ptr<ResourceHandler> handler,
                                const std::string& payload_for_old_handler);
 
-  bool ReplayReadCompleted(bool* defer);
-  void CallReplayReadCompleted();
-
   bool MustDownload();
 
-  // Copies data from |read_buffer_| to |next_handler_|.
-  bool CopyReadBufferToNextHandler();
-
   // Called on the IO thread once the list of plugins has been loaded.
   void OnPluginsLoaded(const std::vector<WebPluginInfo>& plugins);
 
-  enum State {
-    STATE_STARTING,
+  bool CopyReadBufferToNextHandler();
 
-    // In this state, we are filling read_buffer_ with data for the purpose
-    // of sniffing the mime type of the response.
-    STATE_BUFFERING,
-
-    // In this state, we are select an appropriate downstream ResourceHandler
-    // based on the mime type of the response.  We are also potentially waiting
-    // for plugins to load so that we can determine if a plugin is available to
-    // handle the mime type.
-    STATE_PROCESSING,
-
-    // In this state, we are replaying buffered events (OnResponseStarted and
-    // OnReadCompleted) to the downstream ResourceHandler.
-    STATE_REPLAYING,
-
-    // In this state, we are just a blind pass-through ResourceHandler.
-    STATE_STREAMING
-  };
   State state_;
 
-  scoped_refptr<ResourceResponse> response_;
   ResourceDispatcherHostImpl* host_;
 #if defined(ENABLE_PLUGINS)
   PluginService* plugin_service_;
 #endif
-  scoped_refptr<net::IOBuffer> read_buffer_;
-  int read_buffer_size_;
-  int bytes_read_;
+
+  bool switched_handler_;
 
   bool must_download_;
   bool must_download_is_set_;
 
-  base::WeakPtrFactory<MimeTypeResourceHandler> weak_ptr_factory_;
+  // Used to copy data to the new next ResourceHandler.
+  scoped_refptr<ResourceResponse> response_;
+  scoped_refptr<net::IOBuffer> read_buffer_;
+  int bytes_read_;
 
-  DISALLOW_COPY_AND_ASSIGN(MimeTypeResourceHandler);
+  base::WeakPtrFactory<InterceptingResourceHandler> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(InterceptingResourceHandler);
 };
 
 }  // namespace content
 
-#endif  // CONTENT_BROWSER_LOADER_MIME_TYPE_RESOURCE_HANDLER_H_
+#endif  // CONTENT_BROWSER_LOADER_INTERCEPTING_RESOURCE_HANDLER_H_