Introduce BeforeCallEnteredCallback.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 081b6c3810793b92dab625578727e46271689588..ed0f5c16e45b165651f9f19307229cfc0372318b 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -5009,7 +5009,8 @@ typedef void (*MemoryAllocationCallback)(ObjectSpace space,
                                          AllocationAction action,
                                          int size);
 
-// --- Leave Script Callback ---
+// --- Enter/Leave Script Callback ---
+typedef void (*BeforeCallEnteredCallback)(Isolate*);

[jochen (gone - plz use gerrit), 2016/02/17 12:58:48]

what's the reason we need an isolate ptr here, but not on the call completed
callback?

[dgozman, 2016/02/17 16:51:12]

Passing isolate replaces the need to call Isolate::GetCurrent from inside the
callback. I think that's a cleaner contract which does not assume anything about
entered isolate before making a call.

 typedef void (*CallCompletedCallback)();

[jochen (gone - plz use gerrit), 2016/02/18 13:48:38]

can you add an isolate* parameter here as well then?

you can typedef void (*DeprecatedCallCompletedCallback)(); and then overload the
methods to add and remove the callback.

Due to C calling conventions, it's safe to reinterpret_cast<> the deprecated to
a new one internally

[dgozman, 2016/02/19 01:59:42]

Done.

 
 // --- Promise Reject Callback ---
@@ -5810,6 +5811,19 @@ class V8_EXPORT Isolate {
   void SetEventLogger(LogEventCallback that);
 
   /**
+   * Adds a callback to notify the host application right before a script
+   * is about to run. If a script re-enters the runtime during executing, the
+   * BeforeCallEnteredCallback is invoked for each re-entrance.
+   * Executing scripts inside the callback will re-trigger the callback.
+   */
+  void AddBeforeCallEnteredCallback(BeforeCallEnteredCallback callback);
+
+  /**
+   * Removes callback that was installed by AddBeforeCallEnteredCallback.
+   */
+  void RemoveBeforeCallEnteredCallback(BeforeCallEnteredCallback callback);
+
+  /**
    * Adds a callback to notify the host application when a script finished
    * running.  If a script re-enters the runtime during executing, the
    * CallCompletedCallback is only invoked when the outer-most script
@@ -5823,7 +5837,6 @@ class V8_EXPORT Isolate {
    */
   void RemoveCallCompletedCallback(CallCompletedCallback callback);
 
-
   /**
    * Set callback to notify about promise reject with no handler, or
    * revocation of such a previous notification once the handler is added.