Uncommit free pages in all spaces on low memory notification.

BUG=v8:1669
TEST=
R=erik.corry@gmail.com

Review URL: http://codereview.chromium.org/8969017

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10289 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.cc

@@ -463,6 +463,8 @@ void Heap::CollectAllAvailableGarbage() {
   }
   mark_compact_collector()->SetFlags(kNoGCFlags);
   new_space_.Shrink();
+  UncommitFromSpace();
+  Shrink();
   incremental_marking()->UncommitMarkingDeque();
 }