When InterceptingResourceHandler swaps in a handler, call OnWillStart.

content/browser/loader/intercepting_resource_handler.h

 // 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_INTERCEPTING_RESOURCE_HANDLER_H_
 #define CONTENT_BROWSER_LOADER_INTERCEPTING_RESOURCE_HANDLER_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 63 matching lines @@
     // 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,
 
     // The InterceptingResourceHandler is sending the payload given via
     // UseNewHandler to the old handler and waiting for its completion via
     // Resume().
     SENDING_PAYLOAD_TO_OLD_HANDLER,
 
-    // The InterceptingResourcHandler is notifying OnResponseStarted to the new
-    // handler and waiting for its completion via Resume(). After the
-    // completion, the InterceptingResourcHandler will transit to
+    // The InterceptingResourcHandler is calling the new handler's
+    // OnResponseStarted method and waiting for its completion via Resume().
+    // After completion, the InterceptingResourceHandler will transition to
+    // SENDING_ON_RESPONSE_STARTED_TO_NEW_HANDLER on success.
+    SENDING_ON_WILL_START_TO_NEW_HANDLER,
+
+    // The InterceptingResourcHandler is calling the new handler's
+    // OnResponseStarted method and waiting for its completion via Resume().
+    // After completion, the InterceptingResourceHandler will transition to
     // WAITING_FOR_ON_READ_COMPLETED on success.
-    NOTIFYING_ON_RESPONSE_STARTED_TO_NEW_HANDLER,
+    SENDING_ON_RESPONSE_STARTED_TO_NEW_HANDLER,
 
     // The InterceptingResourcHandler is waiting for OnReadCompleted to be
     // called.
     WAITING_FOR_ON_READ_COMPLETED,
 
     // The InterceptingResourceHandler is sending the old handler's contents to
     // the new handler and waiting for its completion via Resume().
     SENDING_BUFFER_TO_NEW_HANDLER,
 
     // 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.
     PASS_THROUGH,
   };
 
   // Runs necessary operations depending on |state_|. Returns false when an
   // error happens, and set |*defer| to true if the operation continues upon
   // return.
   bool DoLoop(bool* defer);
 
   // The return value and |defer| has the same meaning as DoLoop.
   bool SendPayloadToOldHandler(bool* defer);
   bool SendFirstReadBufferToNewHandler(bool* defer);
-  bool SendCompletionToOldHandler(bool* defer);
+  bool SendOnResponseStartedToNewHandler(bool* defer);
 
   State state_ = State::STARTING;
 
   std::unique_ptr<ResourceHandler> new_handler_;
   std::string payload_for_old_handler_;
   size_t payload_bytes_written_ = 0;
 
   // Result of the first read, that may have to be passed to an alternate
   // ResourceHandler instead of the original ResourceHandler.
   scoped_refptr<net::IOBuffer> first_read_buffer_;
   // Instead of |first_read_buffer_|, this handler creates a new IOBuffer with
   // the same size and return it to the client.
   scoped_refptr<net::IOBuffer> first_read_buffer_double_;
   size_t first_read_buffer_size_ = 0;
   size_t first_read_buffer_bytes_read_ = 0;
   size_t first_read_buffer_bytes_written_ = 0;
 
   scoped_refptr<ResourceResponse> response_;
 
   DISALLOW_COPY_AND_ASSIGN(InterceptingResourceHandler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_INTERCEPTING_RESOURCE_HANDLER_H_