Introduce SynchronizedScope to allow heap access from compiler thread.

src/execution.cc

Index: src/execution.cc
diff --git a/src/execution.cc b/src/execution.cc
index 690a4e3f4e6cd8570a0b052ee643b8fedb24aa69..b967e9f8ff6eb717deeca4ef303236645a33f259 100644
--- a/src/execution.cc
+++ b/src/execution.cc
@@ -503,6 +503,22 @@ void StackGuard::RequestInstallCode() {
 }
 
 
+bool StackGuard::IsCompilerSyncRequest() {
+  ExecutionAccess access(isolate_);
+  return (thread_local_.interrupt_flags_ & COMPILER_SYNC) != 0;
+}
+
+
+void StackGuard::RequestCompilerSync() {
+  ExecutionAccess access(isolate_);
+  thread_local_.interrupt_flags_ |= COMPILER_SYNC;
+  if (thread_local_.postpone_interrupts_nesting_ == 0) {
+    thread_local_.jslimit_ = thread_local_.climit_ = kInterruptLimit;
+    isolate_->heap()->SetStackLimits();
+  }
+}
+
+
 bool StackGuard::IsFullDeopt() {
   ExecutionAccess access(isolate_);
   return (thread_local_.interrupt_flags_ & FULL_DEOPT) != 0;
@@ -1049,7 +1065,13 @@ MaybeObject* Execution::HandleStackGuardInterrupt(Isolate* isolate) {
     stack_guard->Continue(INSTALL_CODE);
     isolate->optimizing_compiler_thread()->InstallOptimizedFunctions();
   }
-  isolate->runtime_profiler()->OptimizeNow();
+  if (stack_guard->IsCompilerSyncRequest()) {
+    ASSERT(isolate->concurrent_recompilation_enabled());
+    stack_guard->Continue(COMPILER_SYNC);
+    isolate->optimizing_compiler_thread()->YieldToCompilerThread();
+  } else {
+    isolate->runtime_profiler()->OptimizeNow();
+  }
   return isolate->heap()->undefined_value();
 }