Add metrics to track HTTP/0.9 usage for main frames and subresources

net/http/http_response_info.h

 // Copyright (c) 2011 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 NET_HTTP_HTTP_RESPONSE_INFO_H_
 #define NET_HTTP_HTTP_RESPONSE_INFO_H_
 
 #include <string>
 
 #include "base/time/time.h"
@@ skipping 16 matching lines @@
 
 class NET_EXPORT HttpResponseInfo {
  public:
   // Describes the kind of connection used to fetch this response.
   //
   // NOTE: Please keep in sync with Net.HttpResponseInfo.ConnectionInfo
   // histogram.  Because of that, and also because these values are persisted to
   // the cache, please make sure not to delete or reorder values.
   enum ConnectionInfo {
     CONNECTION_INFO_UNKNOWN = 0,
-    CONNECTION_INFO_HTTP1 = 1,
+    CONNECTION_INFO_HTTP1 = 1,  // HTTP/1.0 or HTTP/1.1.

[Bence, 2016/06/30 21:20:11]

Since you are touching this part of the code anyway, I think it might be
worthwhile to split this further into separate HTTP/1.0 and HTTP/1.1 values.

[mmenke, 2016/06/30 22:18:07]

Done.  They're similar enough to each other, that I wasn't sure it was worth the
effort, but it doesn't hurt.  Did turn up a case where we're now randomly
returning one of the three.

     CONNECTION_INFO_DEPRECATED_SPDY2 = 2,
     CONNECTION_INFO_SPDY3 = 3,
     CONNECTION_INFO_HTTP2 = 4,  // HTTP/2.
     CONNECTION_INFO_QUIC1_SPDY3 = 5,
     CONNECTION_INFO_HTTP2_14 = 6,  // HTTP/2 draft-14.
     CONNECTION_INFO_HTTP2_15 = 7,  // HTTP/2 draft-15.
+    CONNECTION_INFO_HTTP0_9 = 8,
     NUM_OF_CONNECTION_INFOS,
   };
 
   HttpResponseInfo();
   HttpResponseInfo(const HttpResponseInfo& rhs);
   ~HttpResponseInfo();
   HttpResponseInfo& operator=(const HttpResponseInfo& rhs);
   // Even though we could get away with the copy ctor and default operator=,
   // that would prevent us from doing a bunch of forward declaration.
 
@@ skipping 103 matching lines @@
   scoped_refptr<IOBufferWithSize> metadata;
 
   static ConnectionInfo ConnectionInfoFromNextProto(NextProto next_proto);
 
   static std::string ConnectionInfoToString(ConnectionInfo connection_info);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_RESPONSE_INFO_H_