Add uma stats to help evaluate the impact of changes to the quota allocation logic.

content/browser/cache_storage/cache_storage_cache.cc

Index: content/browser/cache_storage/cache_storage_cache.cc
diff --git a/content/browser/cache_storage/cache_storage_cache.cc b/content/browser/cache_storage/cache_storage_cache.cc
index 9a4a02e6d224190a8c369e2aee3a28709ca1bc34..a120339b5d9c1bccf7d60979c248d805a032b29f 100644
--- a/content/browser/cache_storage/cache_storage_cache.cc
+++ b/content/browser/cache_storage/cache_storage_cache.cc
@@ -38,6 +38,7 @@
 #include "storage/browser/blob/blob_storage_context.h"
 #include "storage/browser/blob/blob_url_request_job_factory.h"
 #include "storage/browser/quota/quota_manager_proxy.h"
+#include "storage/common/storage_histograms.h"
 #include "third_party/WebKit/public/platform/modules/serviceworker/WebServiceWorkerResponseType.h"
 
 namespace content {
@@ -47,6 +48,8 @@ namespace {
 const size_t kMaxQueryCacheResultBytes =
     1024 * 1024 * 10;  // 10MB query cache limit
 
+const char kRecordBytesLabel[] = "DiskCache.CacheStorage";
+
 // This class ensures that the cache and the entry have a lifetime as long as
 // the blob that is created to contain them.
 class CacheStorageCacheDataHandle
@@ -185,6 +188,9 @@ void ReadMetadataDidReadMetadata(disk_cache::Entry* entry,
     return;
   }
 
+  if (rv > 0)
+    storage::RecordBytesRead(kRecordBytesLabel, rv);
+
   std::unique_ptr<proto::CacheMetadata> metadata(new proto::CacheMetadata());
 
   if (!metadata->ParseFromArray(buffer->data(), buffer->size())) {
@@ -1002,6 +1008,9 @@ void CacheStorageCache::WriteSideDataDidWrite(const ErrorCallback& callback,
     return;
   }
 
+  if (rv > 0)
+    storage::RecordBytesWritten(kRecordBytesLabel, rv);
+
   UpdateCacheSize(base::Bind(callback, CACHE_STORAGE_OK));
 }
 
@@ -1173,6 +1182,9 @@ void CacheStorageCache::PutDidWriteHeaders(
     return;
   }
 
+  if (rv > 0)
+    storage::RecordBytesWritten(kRecordBytesLabel, rv);
+
   // The metadata is written, now for the response content. The data is streamed
   // from the blob into the cache entry.