Reland "Trigger exception debug event for promises at the throw site."

src/debug.h

Index: src/debug.h
diff --git a/src/debug.h b/src/debug.h
index 7781d4a0ea63df58d45c9b4a8057531baab4de0b..292aff0800032439efc7cc855841c2a966a4d0e2 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -235,6 +235,12 @@ class Debug {
   void FloodHandlerWithOneShot();
   void ChangeBreakOnException(ExceptionBreakType type, bool enable);
   bool IsBreakOnException(ExceptionBreakType type);
+
+  void PromiseHandlePrologue(Handle<JSFunction> promise_getter);
+  void PromiseHandleEpilogue();
+  // Returns a promise if it does not have a reject handler.
+  Handle<Object> GetPromiseForUncaughtException();
+
   void PrepareStep(StepAction step_action,
                    int step_count,
                    StackFrame::Id frame_id);
@@ -538,6 +544,14 @@ class Debug {
   bool break_on_exception_;
   bool break_on_uncaught_exception_;
 
+  // When a promise is being resolved, we may want to trigger a debug event for
+  // the case we catch a throw.  For this purpose we remember the try-catch
+  // handler address that would catch the exception.  We also hold onto a
+  // closure that returns a promise if the exception is considered uncaught.
+  // Due to the possibility of reentry we use a list to form a stack.
+  List<StackHandler*> promise_catch_handlers_;
+  List<Handle<JSFunction> > promise_getters_;
+
   // Per-thread data.
   class ThreadLocal {
    public:
@@ -774,9 +788,7 @@ class Debugger {
   MUST_USE_RESULT MaybeHandle<Object> MakeScriptCollectedEvent(int id);
 
   void OnDebugBreak(Handle<Object> break_points_hit, bool auto_continue);
-  void OnException(Handle<Object> exception,
-                   bool uncaught,
-                   Handle<Object> promise = Handle<Object>::null());
+  void OnException(Handle<Object> exception, bool uncaught);
   void OnBeforeCompile(Handle<Script> script);
 
   enum AfterCompileFlags {