Remove ResourceLoader PostTask after reading headers.

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 <utility>
 
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
@@ skipping 624 matching lines @@
   scoped_refptr<ResourceResponse> response = new ResourceResponse();
   PopulateResourceResponse(info, request_.get(), response.get());
 
   delegate_->DidReceiveResponse(this);
 
   // TODO(darin): Remove ScopedTracker below once crbug.com/475761 is fixed.
   tracked_objects::ScopedTracker tracking_profile(
       FROM_HERE_WITH_EXPLICIT_FUNCTION("475761 OnResponseStarted()"));
 
   read_deferral_start_time_ = base::TimeTicks::Now();
-  ScopedDeferral scoped_deferral(this, DEFERRED_READ);
+  // Using a ScopedDeferral here would result in calling ReadMore(true) on sync
+  // success. Calling ReadMore(false) here instead allows small responses to be
+  // handled completely synchronously, if no ResourceHandler defers handling of
+  // the response.
+  deferred_stage_ = DEFERRED_SYNC;
   handler_->OnResponseStarted(response.get(),
                               base::MakeUnique<Controller>(this));
+  if (is_deferred()) {
+    deferred_stage_ = DEFERRED_READ;
+  } else {
+    ReadMore(false);
+  }
 }
 
 void ResourceLoader::ReadMore(bool handle_result_async) {
   TRACE_EVENT_WITH_FLOW0("loading", "ResourceLoader::ReadMore", this,
                          TRACE_EVENT_FLAG_FLOW_IN | TRACE_EVENT_FLAG_FLOW_OUT);
   DCHECK(!is_deferred());
 
   // Make sure we track the buffer in at least one place.  This ensures it gets
   // deleted even in the case the request has already finished its job and
   // doesn't use the buffer.
@@ skipping 144 matching lines @@
       UMA_HISTOGRAM_ENUMERATION("Net.Prefetch.Pattern", prefetch_status,
                                 STATUS_MAX);
     }
   } else if (request_->response_info().unused_since_prefetch) {
     TimeDelta total_time = base::TimeTicks::Now() - request_->creation_time();
     UMA_HISTOGRAM_TIMES("Net.Prefetch.TimeSpentOnPrefetchHit", total_time);
   }
 }
 
 }  // namespace content