Support tasks injection into a running VM.

include/v8-debug.h

Index: include/v8-debug.h
diff --git a/include/v8-debug.h b/include/v8-debug.h
index 6abf4e095bccadacdb6ef3fa4a3fc06fcbc76966..9be5c2d49002d65d4463fd1d9ec7f3aa122c90d2 100644
--- a/include/v8-debug.h
+++ b/include/v8-debug.h
@@ -177,6 +177,17 @@ class V8_EXPORT Debug {
   // stops.
   static void DebugBreakForCommand(Isolate* isolate, ClientData* data);
 
+  class Task {
+   public:
+    virtual void Run() = 0;
+    virtual ~Task() {}
+  };
+
+  // Break execution of JavaScript in the given isolate (this method
+  // can be invoked from a non-VM thread) and execute the given task on the
+  // VM thread. The VM takes ownership of the task.
+  static void BreakAndRun(Isolate* isolate, Task* task);
+
   // Message based interface. The message protocol is JSON.
   static void SetMessageHandler(MessageHandler handler);