Add PNACL_CACHE cache backend type, and allow larger files for this type.

net/base/cache_type.h

Index: net/base/cache_type.h
diff --git a/net/base/cache_type.h b/net/base/cache_type.h
index 69b5646ece7ec6fd2ff194aba6674b8d4098e5b7..06aa826b8fb75946379d53d28a571066d5971b3d 100644
--- a/net/base/cache_type.h
+++ b/net/base/cache_type.h
@@ -13,7 +13,8 @@ enum CacheType {
   MEMORY_CACHE,  // Data is stored only in memory.
   MEDIA_CACHE,  // Optimized to handle media files.
   APP_CACHE,  // Backing store for an AppCache.
-  SHADER_CACHE  // Backing store for the GL shader cache.
+  SHADER_CACHE, // Backing store for the GL shader cache.
+  PNACL_CACHE, // Backing store the PNaCl translation cache
 };
 
 // The types of disk cache backend, only used at backend instantiation.