Make assertion scopes thread safe.

src/compiler.cc

Index: src/compiler.cc
diff --git a/src/compiler.cc b/src/compiler.cc
index b799a5a6ef1808b11d1b7f190b69a74be4cfa0f9..1334f5aaf4194905c70247442e85e486f137dcbb 100644
--- a/src/compiler.cc
+++ b/src/compiler.cc
@@ -393,9 +393,9 @@ OptimizingCompiler::Status OptimizingCompiler::CreateGraph() {
 }
 
 OptimizingCompiler::Status OptimizingCompiler::OptimizeGraph() {
-  AssertNoAllocation no_gc;
-  NoHandleAllocation no_handles(isolate());
-  HandleDereferenceGuard no_deref(isolate(), HandleDereferenceGuard::DISALLOW);
+  DisallowHeapAllocation no_allocation;
+  DisallowHandleAllocation no_handles;
+  DisallowHandleDereference no_deref;
 
   ASSERT(last_status() == SUCCEEDED);
   Timer t(this, &time_taken_to_optimize_);
@@ -424,8 +424,7 @@ OptimizingCompiler::Status OptimizingCompiler::GenerateAndInstallCode() {
     // graph creation.  To make sure that we don't encounter inconsistencies
     // between graph creation and code generation, we disallow accessing
     // objects through deferred handles during the latter, with exceptions.
-    HandleDereferenceGuard no_deref_deferred(
-        isolate(), HandleDereferenceGuard::DISALLOW_DEFERRED);
+    DisallowDeferredHandleDereference no_deferred_handle_deref();
     Handle<Code> optimized_code = chunk_->Codegen();
     if (optimized_code.is_null()) {
       info()->set_bailout_reason("code generation failed");