Speed-up 'new TypedArray(arrayLike)'.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 6b1815383314046ef429acc68dd43c6c7a489335..50019497f8eae6174c40831297ef0100af4c8ba2 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -2410,8 +2410,20 @@ class V8EXPORT ArrayBuffer : public Object {
 
     /**
      * Allocate |length| bytes. Return NULL if allocation is not successful.
+     * Memory should be initialized to zeroes.
      */
     virtual void* Allocate(size_t length) = 0;
+
+    /**
+     * Allocate |length| bytes. Return NULL if allocation is not successful.
+     * Memory does not have to be initialized.
+     */
+    virtual void* AllocateUninitialized(size_t length) {
+      // Override with call to |Allocate| for compatibility
+      // with legacy version.
+      return Allocate(length);
+    }
+
     /**
      * Free the memory pointed to |data|. That memory is guaranteed to be
      * previously allocated by |Allocate|.