Parallel recompilation: fewer handle dereferences and tighter checks.

src/code-stubs-hydrogen.cc

Index: src/code-stubs-hydrogen.cc
diff --git a/src/code-stubs-hydrogen.cc b/src/code-stubs-hydrogen.cc
index bb8bfe3fdc4447e90683ffc8df0cf77514ae1cd5..b22d20356e8f62f5af681335432ed7faf893c7ac 100644
--- a/src/code-stubs-hydrogen.cc
+++ b/src/code-stubs-hydrogen.cc
@@ -39,7 +39,7 @@ static LChunk* OptimizeGraph(HGraph* graph) {
   Isolate* isolate =  graph->isolate();
   AssertNoAllocation no_gc;
   NoHandleAllocation no_handles(isolate);
-  NoHandleDereference no_deref(isolate);
+  HandleDereferenceGuard no_deref(isolate, HandleDereferenceGuard::DISALLOW);
 
   ASSERT(graph != NULL);
   SmartArrayPointer<char> bailout_reason;