Determine prevalence of cache-control: no-store in main frame resources.

content/browser/loader/resource_dispatcher_host_impl.cc

Index: content/browser/loader/resource_dispatcher_host_impl.cc
diff --git a/content/browser/loader/resource_dispatcher_host_impl.cc b/content/browser/loader/resource_dispatcher_host_impl.cc
index 86d5e5fb1fff831c54dc35f149a56a55cb0979df..868f97ebb6d80db68fdc3e25c3db701c8294bd13 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -317,6 +317,14 @@ webkit_blob::BlobStorageContext* GetBlobStorageContext(
   return filter->blob_storage_context()->context();
 }
 
+enum CacheStorable {
+  // A "cache-control: no-store" header was found.
+  CACHE_STORABLE_NO_STORE,
+  // No "no-store" header was found.
+  CACHE_STORABLE_STORE,
+  CACHE_STORABLE_MAX
+};
+
 }  // namespace
 
 // static
@@ -769,6 +777,17 @@ void ResourceDispatcherHostImpl::DidFinishLoading(ResourceLoader* loader) {
       UMA_HISTOGRAM_COUNTS_100(
           "Net.CertificateTransparency.MainFrameValidSCTCount", num_valid_scts);
     }
+
+    net::HttpResponseHeaders* response_headers =
+        loader->request()->response_headers();
+    if (response_headers) {
+      CacheStorable storable =
+          response_headers->HasHeaderValue("cache-control", "no-store")
+              ? CACHE_STORABLE_NO_STORE
+              : CACHE_STORABLE_STORE;

[davidben, 2014/06/11 16:28:01]

This could also just be a boolean with UMA_HISTOGRAM_BOOLEAN. The enum thing
with 0 or 1 will still work I believe.

[jkarlin, 2014/06/11 16:50:06]

True, that's simpler.  Went with BOOLEAN.

+      UMA_HISTOGRAM_ENUMERATION(
+          "Net.MainFrameStorable", storable, CACHE_STORABLE_MAX);
+    }
   } else {
     if (info->GetResourceType() == ResourceType::IMAGE) {
       UMA_HISTOGRAM_SPARSE_SLOWLY(