Eliminate Assertions.h's dependency on Types.h, for a narrower interface and minimized dependencies. No bug, r=Ms2ger

mfbt/Assertions.h

@@ -9,8 +9,8 @@
 #define mozilla_Assertions_h_
 
 #include "mozilla/Attributes.h"
-#include "mozilla/Types.h"
 
+#include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
 #ifdef WIN32

mfbt/HashFunctions.cpp

@@ -6,6 +6,7 @@
 /* Implementations of hash functions. */
 
 #include "mozilla/HashFunctions.h"
+#include "mozilla/Types.h"
 
 #include <string.h>
 

mfbt/HashFunctions.h

@@ -48,6 +48,7 @@
 #include "mozilla/Assertions.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/StandardInteger.h"
+#include "mozilla/Types.h"
 
 #ifdef __cplusplus
 namespace mozilla {