Add histograms to ResourceFetcher to measure memory cache hit rate.

Source/core/fetch/Resource.h

Index: Source/core/fetch/Resource.h
diff --git a/Source/core/fetch/Resource.h b/Source/core/fetch/Resource.h
index 6d5526b8db38b98471d56c4fdcf1f900af7ce760..4867785d4a678131ca54e21eae2eed82f3f4b78d 100644
--- a/Source/core/fetch/Resource.h
+++ b/Source/core/fetch/Resource.h
@@ -58,7 +58,7 @@ class Resource {
 
 public:
     enum Type {
-        MainResource,
+        MainResource = 0,

[abarth-chromium, 2013/09/13 17:38:18]

This change doesn't do anything.

[Philippe, 2013/09/16 11:47:21]

Done.

         Image,
         CSSStyleSheet,
         Script,
@@ -70,7 +70,8 @@ public:
         LinkSubresource,
         TextTrack,
         Shader,
-        ImportResource
+        ImportResource,
+        TypeBoundaryValue = 13, // Used for histograms.

[abarth-chromium, 2013/09/13 17:38:18]

What is TypeBoundaryValue?  Perhaps you mean NumberOfTypes?

Also, no need for this comment.  Folks can grep the code to see where this value
is used.

[Philippe, 2013/09/16 11:47:21]

Done.

     };
 
     enum Status {