Introduce SynchronizedScope to allow heap access from compiler thread.

src/execution.h

Index: src/execution.h
diff --git a/src/execution.h b/src/execution.h
index b53a83358cd21ac0dfaa431bfa8e3092c960e02a..1466e3e75753bdc9943d70543e46f5b678f9986f 100644
--- a/src/execution.h
+++ b/src/execution.h
@@ -45,7 +45,8 @@ enum InterruptFlag {
   FULL_DEOPT = 1 << 6,
   INSTALL_CODE = 1 << 7,
   API_INTERRUPT = 1 << 8,
-  DEOPT_MARKED_ALLOCATION_SITES = 1 << 9
+  DEOPT_MARKED_ALLOCATION_SITES = 1 << 9,
+  COMPILER_SYNC = 1 << 10
 };
 
 
@@ -221,6 +222,8 @@ class StackGuard {
   void RequestGC();
   bool IsInstallCodeRequest();
   void RequestInstallCode();
+  bool IsCompilerSyncRequest();
+  void RequestCompilerSync();
   bool IsFullDeopt();
   void FullDeopt();
   bool IsDeoptMarkedAllocationSites();