Switch profiler from isolates to threads [second landing]

runtime/include/dart_api.h

Index: runtime/include/dart_api.h
diff --git a/runtime/include/dart_api.h b/runtime/include/dart_api.h
index e79a5755038df1a0dfed9296ff28577c00cc312a..29826af16ee46a305255b3649f4bdcdf7c70a045 100755
--- a/runtime/include/dart_api.h
+++ b/runtime/include/dart_api.h
@@ -1027,14 +1027,25 @@ DART_EXPORT Dart_Handle Dart_DebugName();
 DART_EXPORT void Dart_EnterIsolate(Dart_Isolate isolate);
 
 /**
- * Notifies the VM that the current isolate is about to make a blocking call.
+ * Notifies the VM that the current thread should not be profiled until a
+ * matching call to Dart_ThreadEnableProfiling is made.
+ *
+ * NOTE: By default, if a thread has entered an isolate it will be profiled.
+ * This function should be used when an embedder knows a thread is about
+ * to make a blocking call and wants to avoid unnecessary interrupts by
+ * the profiler.
  */
-DART_EXPORT void Dart_IsolateBlocked();
+DART_EXPORT void Dart_ThreadDisableProfiling();
 
 /**
- * Notifies the VM that the current isolate is no longer blocked.
+ * Notifies the VM that the current thread should be profiled.
+ *
+ * NOTE: It is only legal to call this function *after* calling
+ *   Dart_ThreadDisableProfiling.
+ *
+ * NOTE: By default, if a thread has entered an isolate it will be profiled.
  */
-DART_EXPORT void Dart_IsolateUnblocked();
+DART_EXPORT void Dart_ThreadEnableProfiling();
 
 /**
  * Exits an isolate. After this call, Dart_CurrentIsolate will