Add histograms to ResourceFetcher to measure memory cache hit rate.

Source/core/fetch/ResourceFetcher.cpp

Index: Source/core/fetch/ResourceFetcher.cpp
diff --git a/Source/core/fetch/ResourceFetcher.cpp b/Source/core/fetch/ResourceFetcher.cpp
index 605967270e987fe01f0348d5ef04a2d3eb21e3dd..b1247d988e137dde51fc11f00916d5650de2e375 100644
--- a/Source/core/fetch/ResourceFetcher.cpp
+++ b/Source/core/fetch/ResourceFetcher.cpp
@@ -59,6 +59,7 @@
 #include "core/page/Performance.h"
 #include "core/page/ResourceTimingInfo.h"
 #include "core/page/Settings.h"
+#include "core/platform/HistogramSupport.h"
 #include "core/platform/Logging.h"
 #include "core/platform/chromium/TraceEvent.h"
 #include "public/platform/Platform.h"
@@ -71,8 +72,17 @@
 #define PRELOAD_DEBUG 0
 
 namespace WebCore {
+namespace {

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

We usually have a blank line above anonymous namespaces.

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

Done.

 
-static Resource* createResource(Resource::Type type, const ResourceRequest& request, const String& charset)
+// Used for histograms.

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

No need for this comment.

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

Done.

+enum ActionUponResourceRequest {
+    LoadResource = 0,
+    RevalidateResource = 1,
+    UseResourceFromCache = 2,
+    ActionUponResourceRequestBoundaryValue = 3,

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

No need to list these numbers explicitly.

What is a boundary value?  How about NumberOfResourceRequestActions?

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

Boundary value is the terminology used in HistogramSupport.h. I agree it's not
very clear :)

+};
+
+Resource* createResource(Resource::Type type, const ResourceRequest& request, const String& charset)
 {
     switch (type) {
     case Resource::Image:
@@ -106,7 +116,7 @@ static Resource* createResource(Resource::Type type, const ResourceRequest& requ
     return 0;
 }
 
-static ResourceLoadPriority loadPriority(Resource::Type type, const FetchRequest& request)
+ResourceLoadPriority loadPriority(Resource::Type type, const FetchRequest& request)
 {
     if (request.priority() != ResourceLoadPriorityUnresolved)
         return request.priority();
@@ -140,7 +150,7 @@ static ResourceLoadPriority loadPriority(Resource::Type type, const FetchRequest
     return ResourceLoadPriorityUnresolved;
 }
 
-static Resource* resourceFromDataURIRequest(const ResourceRequest& request)
+Resource* resourceFromDataURIRequest(const ResourceRequest& request)
 {
     const KURL& url = request.url();
     ASSERT(url.protocolIsData());
@@ -161,6 +171,8 @@ static Resource* resourceFromDataURIRequest(const ResourceRequest& request)
     return resource;
 }
 
+} // namespace
+
 ResourceFetcher::ResourceFetcher(DocumentLoader* documentLoader)
     : m_document(0)
     , m_documentLoader(documentLoader)
@@ -541,13 +553,27 @@ ResourcePtr<Resource> ResourceFetcher::requestResource(Resource::Type type, Fetc
         // Fall through
     case Load:
         resource = loadResource(type, request, request.charset());
+        HistogramSupport::histogramEnumeration(
+            "Renderer.ResourceFetcher.ActionUponResourceRequest", LoadResource,

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

Renderer -> WebCore

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

Done.

+            ActionUponResourceRequestBoundaryValue);
         break;
     case Revalidate:
         resource = revalidateResource(request, resource.get());
+        HistogramSupport::histogramEnumeration(
+            "Renderer.ResourceFetcher.ActionUponResourceRequest", RevalidateResource,
+            ActionUponResourceRequestBoundaryValue);
         break;
     case Use:
         resource->updateForAccess();
         notifyLoadedFromMemoryCache(resource.get());
+        HistogramSupport::histogramEnumeration(
+            "Renderer.ResourceFetcher.ActionUponResourceRequest", UseResourceFromCache,
+            ActionUponResourceRequestBoundaryValue);
+        HistogramSupport::histogramEnumeration(
+            "Renderer.ResourceFetcher.ResourceHasClientUponCacheHit", resource->hasClients(), 2);
+        HistogramSupport::histogramEnumeration(
+            "Renderer.ResourceFetcher.ResourceTypeUponCacheHit", resource->type(),
+            Resource::TypeBoundaryValue);
         break;
     }