Replace OS::MemCopy with memcpy in typed array initialization.

This is an attempt to fix a weird perf regression on MacOS X 10.6 bot.
Perf regression is not reproducible on MacOS X 10.8.
This difference in memory-copying routines is the only reasonable
difference in the algorithm. We should try and see.

R=bmeurer@chromium.org
BUG=270642

Review URL: https://codereview.chromium.org/23330005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16245 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/runtime.cc

@@ -996,7 +996,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArrayInitializeFromArrayLike) {
           JSArrayBuffer::cast(typed_array->buffer())->backing_store());
       size_t source_byte_offset =
           NumberToSize(isolate, typed_array->byte_offset());
-      OS::MemCopy(
+      memcpy(
           buffer->backing_store(),
           backing_store + source_byte_offset,
           byte_length);