Use string16 for cache_name in the back end of CacheStorage.

content/browser/cache_storage/cache_storage.proto

Index: content/browser/cache_storage/cache_storage.proto
diff --git a/content/browser/cache_storage/cache_storage.proto b/content/browser/cache_storage/cache_storage.proto
index 07a61700cff974fb1b38d568f576da0f15fbd8b3..0686126db4de95d0d3352f4974d04e1ef330cff7 100644
--- a/content/browser/cache_storage/cache_storage.proto
+++ b/content/browser/cache_storage/cache_storage.proto
@@ -12,6 +12,8 @@ message CacheStorageIndex {
   message Cache {
     required string name = 1;
     optional string cache_dir = 2;
+    // To support UTF-16 properly, we use bytes type. See crbug.com/432746.
+    optional bytes name_utf16 = 3;
   }
   repeated Cache cache = 1;
   optional string origin = 2;