Add UMA histograms to AsyncResourceHandler to track content size.

content/browser/loader/async_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.
 
 #ifndef CONTENT_BROWSER_LOADER_ASYNC_RESOURCE_HANDLER_H_
 #define CONTENT_BROWSER_LOADER_ASYNC_RESOURCE_HANDLER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 60 matching lines @@
 
   scoped_refptr<ResourceBuffer> buffer_;
   ResourceDispatcherHostImpl* rdh_;
 
   // Number of messages we've sent to the renderer that we haven't gotten an
   // ACK for. This allows us to avoid having too many messages in flight.
   int pending_data_count_;
 
   int allocation_size_;
 
+  // Size of received body. Used for comparison with expected content size,
+  // which is reported to UMA.
+  int64_t total_read_bytes_;

[mmenke, 2017/01/11 20:25:20]

Maybe total_read_body_bytes_?

+
   bool first_chunk_read_ = false;
 
   bool did_defer_;
 
   bool has_checked_for_sufficient_resources_;
   bool sent_received_response_msg_;
   bool sent_data_buffer_msg_;
 
   std::unique_ptr<InliningHelper> inlining_helper_;
   base::TimeTicks response_started_ticks_;
 
   std::unique_ptr<UploadProgressTracker> upload_progress_tracker_;
 
   int64_t reported_transfer_size_;
 
   DISALLOW_COPY_AND_ASSIGN(AsyncResourceHandler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_ASYNC_RESOURCE_HANDLER_H_