Initial isolate reload support

runtime/vm/compiler.h

Index: runtime/vm/compiler.h
diff --git a/runtime/vm/compiler.h b/runtime/vm/compiler.h
index e995620ba4fc8475fca5bb25fd9cda9d22a147a9..1e8e3fc5be880b296ed01b1162daca8c9edc28c4 100644
--- a/runtime/vm/compiler.h
+++ b/runtime/vm/compiler.h
@@ -163,8 +163,15 @@ class BackgroundCompiler : public ThreadPool::Task {
   static void EnsureInit(Thread* thread);
 
   // Stops background compiler of the given isolate.
+  // TODO(turnidge): Give Stop and Disable more distinct names.
   static void Stop(Isolate* isolate);
 
+  static void Disable();
+
+  static void Enable();
+
+  static bool IsDisabled();
+
   // Call to optimize a function in the background, enters the function in the
   // compilation queue.
   void CompileOptimized(const Function& function);