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

content/browser/appcache/appcache_disk_cache.cc

Index: content/browser/appcache/appcache_disk_cache.cc
diff --git a/content/browser/appcache/appcache_disk_cache.cc b/content/browser/appcache/appcache_disk_cache.cc
index f5c718c7de7a2f1668d64bb44977fe90425c779d..16dbe751ef29ae8d10c686c2047ae39032b9d824 100644
--- a/content/browser/appcache/appcache_disk_cache.cc
+++ b/content/browser/appcache/appcache_disk_cache.cc
@@ -317,11 +317,11 @@ int AppCacheDiskCache::DoomEntry(int64_t key,
 }
 
 AppCacheDiskCache::AppCacheDiskCache(bool use_simple_cache)
-    : use_simple_cache_(use_simple_cache),
+    : AppCacheDiskCacheInterface("DiskCache.AppCache"),
+      use_simple_cache_(use_simple_cache),
       is_disabled_(false),
       is_waiting_to_initialize_(false),
-      weak_factory_(this) {
-}
+      weak_factory_(this) {}
 
 AppCacheDiskCache::PendingCall::PendingCall()
     : call_type(CREATE),