Differentiate between small and large images in caching metrics

net/http/http_cache_transaction.cc

Index: net/http/http_cache_transaction.cc
diff --git a/net/http/http_cache_transaction.cc b/net/http/http_cache_transaction.cc
index 178df98d6e1a1876fc748eb89d4bb43202fb284a..933d01c85c58470179f5cdbdd566427743fa323b 100644
--- a/net/http/http_cache_transaction.cc
+++ b/net/http/http_cache_transaction.cc
@@ -2706,8 +2706,8 @@ void HttpCache::Transaction::RecordHistograms() {
   }
 
   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.
@@ -2723,6 +2723,13 @@ void HttpCache::Transaction::RecordHistograms() {
                                 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",