New heap profiler: add support for progress reporting and control.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 8ecf63aebd699b98ee51b3152a2c2003e83800c7..7fd063197e8a28f9f2993624a9a71b181d50dac3 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -3281,6 +3281,24 @@ class V8EXPORT OutputStream {  // NOLINT
 };
 
 
+/**
+ * An interface for reporting progress and controlling long-running
+ * activities.
+ */
+class V8EXPORT ActivityControl {  // NOLINT
+ public:
+  enum ControlOption {
+    kContinue = 0,
+    kAbort = 1
+  };
+  virtual ~ActivityControl() {}
+  /**
+   * Notify about current progress. The activity can be stopped by
+   * returning kAbort as the callback result.
+   */
+  virtual ControlOption ReportProgressValue(int done, int total) = 0;
+};
+
 
 // --- I m p l e m e n t a t i o n ---