Avoid issuing a Read() after draining a request.

content/browser/loader/resource_loader.cc

 // 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.
 
 #include "content/browser/loader/resource_loader.h"
 
 #include "base/command_line.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/time/time.h"
@@ skipping 150 matching lines @@
   }
 }
 
 void ResourceLoader::MarkAsTransferring() {
   CHECK(ResourceType::IsFrame(GetRequestInfo()->GetResourceType()))
       << "Can only transfer for navigations";
   is_transferring_ = true;
 }
 
 void ResourceLoader::CompleteTransfer() {
-  DCHECK_EQ(DEFERRED_READ, deferred_stage_);
+  // Although CrossSiteResourceHandler defers at OnResponseStarted
+  // (DEFERRED_READ), it may be seeing a replay of events via
+  // BufferedResourceHandler, and so the request itself is actually deferred at
+  // a later read stage.
+  DCHECK(DEFERRED_READ == deferred_stage_ ||
+         DEFERRED_RESPONSE_COMPLETE == deferred_stage_);
 
   is_transferring_ = false;
   GetRequestInfo()->cross_site_handler()->ResumeResponse();
 }
 
 ResourceRequestInfoImpl* ResourceLoader::GetRequestInfo() {
   return ResourceRequestInfoImpl::ForRequest(request_.get());
 }
 
 void ResourceLoader::ClearLoginDelegate() {
@@ skipping 174 matching lines @@
   }
 
   CompleteRead(bytes_read);
 
   // If the handler cancelled or deferred the request, do not continue
   // processing the read. If cancelled, the URLRequest has already been
   // cancelled and will schedule an erroring OnReadCompleted later. If deferred,
   // do nothing until resumed.
   //
   // Note: if bytes_read is 0 (EOF) and the handler defers, resumption will call
-  // Read() on the URLRequest again and get a second EOF.
+  // ResponseCompleted().
   if (is_deferred() || !request_->status().is_success())
     return;
 
   if (bytes_read > 0) {
     StartReading(true);  // Read the next chunk.
   } else {
     // URLRequest reported an EOF. Call ResponseCompleted.
     DCHECK_EQ(0, bytes_read);
     ResponseCompleted();
   }
@@ skipping 42 matching lines @@
       break;
     case DEFERRED_REDIRECT:
       request_->FollowDeferredRedirect();
       break;
     case DEFERRED_READ:
       base::MessageLoop::current()->PostTask(
           FROM_HERE,
           base::Bind(&ResourceLoader::ResumeReading,
                      weak_ptr_factory_.GetWeakPtr()));
       break;
+    case DEFERRED_RESPONSE_COMPLETE:
+      base::MessageLoop::current()->PostTask(
+          FROM_HERE,
+          base::Bind(&ResourceLoader::ResponseCompleted,
+                     weak_ptr_factory_.GetWeakPtr()));
+      break;
     case DEFERRED_FINISH:
       // Delay self-destruction since we don't know how we were reached.
       base::MessageLoop::current()->PostTask(
           FROM_HERE,
           base::Bind(&ResourceLoader::CallDidFinishLoading,
                      weak_ptr_factory_.GetWeakPtr()));
       break;
   }
 }
 
@@ skipping 176 matching lines @@
 void ResourceLoader::CompleteRead(int bytes_read) {
   DCHECK(bytes_read >= 0);
   DCHECK(request_->status().is_success());
 
   ResourceRequestInfoImpl* info = GetRequestInfo();
 
   bool defer = false;
   if (!handler_->OnReadCompleted(info->GetRequestID(), bytes_read, &defer)) {
     Cancel();
   } else if (defer) {
-    deferred_stage_ = DEFERRED_READ;  // Read next chunk when resumed.
+    deferred_stage_ =
+        bytes_read > 0 ? DEFERRED_READ : DEFERRED_RESPONSE_COMPLETE;
   }
 
   // Note: the request may still have been cancelled while OnReadCompleted
   // returns true if OnReadCompleted caused request to get cancelled
   // out-of-band. (In AwResourceDispatcherHostDelegate::DownloadStarting, for
   // instance.)
 }
 
 void ResourceLoader::ResponseCompleted() {
   VLOG(1) << "ResponseCompleted: " << request_->url().spec();
@@ skipping 59 matching lines @@
       case net::URLRequestStatus::FAILED:
         status = STATUS_UNDEFINED;
         break;
     }
 
     UMA_HISTOGRAM_ENUMERATION("Net.Prefetch.Pattern", status, STATUS_MAX);
   }
 }
 
 }  // namespace content