Add global setup for runtime profiler.

src/runtime-profiler.h

Index: src/runtime-profiler.h
diff --git a/src/runtime-profiler.h b/src/runtime-profiler.h
index 3656893ae783c556bf1215bba30c4ffc1c057f7d..692b4ffacc29c5e03a7f7f3d312cd641c0d806d0 100644
--- a/src/runtime-profiler.h
+++ b/src/runtime-profiler.h
@@ -44,7 +44,12 @@ class RuntimeProfiler {
  public:
   explicit RuntimeProfiler(Isolate* isolate);
 
-  static bool IsEnabled();
+  static void GlobalSetup();
+
+  static inline bool IsEnabled() {
+    ASSERT(has_been_globally_setup_);
+    return enabled_;
+  }
 
   void OptimizeNow();
   void OptimizeSoon(JSFunction* function);
@@ -143,6 +148,11 @@ class RuntimeProfiler {
   //   0 or positive => the number of isolates running JavaScript code.
   static Atomic32 state_;
   static Semaphore* semaphore_;
+
+#ifdef DEBUG
+  static bool has_been_globally_setup_;
+#endif
+  static bool enabled_;
 };