Bug 1361699 - Add buffer when writing hashstore to file. r=gcp, r=mcmanus, a=RyanVM

We write a lot of 4-bytes prefixes to file which call many system calls.
We should use a buffer and only write to file if the buffer is full or
finish writing. nsIBufferedOutputStream is a good candidate to do that

MozReview-Commit-ID: CzGOd7iXVTv

--HG--
extra : source : 8f2b4efc5f0d3191a7e80d9324933621e111b44a

netwerk/base/nsBufferedStreams.h

@@ -88,10 +88,10 @@ protected:
 
 ////////////////////////////////////////////////////////////////////////////////
 
-class nsBufferedOutputStream final : public nsBufferedStream,
-                                     public nsISafeOutputStream,
-                                     public nsIBufferedOutputStream,
-                                     public nsIStreamBufferAccess
+class nsBufferedOutputStream  : public nsBufferedStream,
+                                public nsISafeOutputStream,
+                                public nsIBufferedOutputStream,
+                                public nsIStreamBufferAccess
 {
 public:
     NS_DECL_ISUPPORTS_INHERITED