Differentiate between small and large images in caching metrics

net/http/http_cache_transaction.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 "net/http/http_cache_transaction.h"
 
 #include "build/build_config.h"  // For OS_POSIX
 
 #if defined(OS_POSIX)
 #include <unistd.h>
@@ skipping 2688 matching lines @@
 
 void HttpCache::Transaction::RecordHistograms() {
   DCHECK_NE(PATTERN_UNDEFINED, transaction_pattern_);
   if (!cache_.get() || !cache_->GetCurrentBackend() ||
       cache_->GetCurrentBackend()->GetCacheType() != DISK_CACHE ||
       cache_->mode() != NORMAL || request_->method != "GET") {
     return;
   }
 
   std::string mime_type;
-  if (GetResponseInfo()->headers &&
-      GetResponseInfo()->headers->GetMimeType(&mime_type)) {
+  HttpResponseHeaders* response_headers = GetResponseInfo()->headers.get();
+  if (response_headers && response_headers->GetMimeType(&mime_type)) {
     // Record the cache pattern by resource type. The type is inferred by
     // response header mime type, which could be incorrect, so this is just an
     // estimate.
     if (mime_type == "text/html" && (request_->load_flags & LOAD_MAIN_FRAME)) {
       UMA_HISTOGRAM_ENUMERATION(std::string("HttpCache.Pattern.MainFrameHTML"),
                                 transaction_pattern_, PATTERN_MAX);
     } else if (mime_type == "text/html") {
       UMA_HISTOGRAM_ENUMERATION(
           std::string("HttpCache.Pattern.NonMainFrameHTML"),
           transaction_pattern_, PATTERN_MAX);
     } else if (mime_type == "text/css") {
       UMA_HISTOGRAM_ENUMERATION(std::string("HttpCache.Pattern.CSS"),
                                 transaction_pattern_, PATTERN_MAX);
     } else if (base::StartsWith(mime_type, "image/",
                                 base::CompareCase::SENSITIVE)) {
+      if (response_headers->GetContentLength() < 100) {

[Deprecated (see juliatuttle), 2016/04/14 14:11:33]

GetContentLength returns -1 if there is no Content-Length header. Do you intend
for those to be considered tiny images?

[jkarlin, 2016/04/14 14:28:52]

Good point, better to skip them. Done.

+        UMA_HISTOGRAM_ENUMERATION(std::string("HttpCache.Pattern.TinyImage"),
+                                  transaction_pattern_, PATTERN_MAX);
+      } else {
+        UMA_HISTOGRAM_ENUMERATION(std::string("HttpCache.Pattern.NonTinyImage"),
+                                  transaction_pattern_, PATTERN_MAX);
+      }
       UMA_HISTOGRAM_ENUMERATION(std::string("HttpCache.Pattern.Image"),
                                 transaction_pattern_, PATTERN_MAX);
     } else if (base::EndsWith(mime_type, "javascript",
                               base::CompareCase::SENSITIVE) ||
                base::EndsWith(mime_type, "ecmascript",
                               base::CompareCase::SENSITIVE)) {
       UMA_HISTOGRAM_ENUMERATION(std::string("HttpCache.Pattern.JavaScript"),
                                 transaction_pattern_, PATTERN_MAX);
     } else if (mime_type.find("font") != std::string::npos) {
       UMA_HISTOGRAM_ENUMERATION(std::string("HttpCache.Pattern.Font"),
@@ skipping 71 matching lines @@
     default:
       NOTREACHED();
   }
 }
 
 void HttpCache::Transaction::OnIOComplete(int result) {
   DoLoop(result);
 }
 
 }  // namespace net