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

test/mjsunit/es6/debug-promises-uncaught-uncaught.js

Index: test/mjsunit/es6/debug-promises-uncaught-uncaught.js
diff --git a/test/mjsunit/es6/debug-promises-uncaught-uncaught.js b/test/mjsunit/es6/debug-promises-uncaught-uncaught.js
index ae58c628cacb7e88e29456cd6fe6ef3f7b45675c..fa97ac0d8598695a327f435d6073bdc33631ec15 100644
--- a/test/mjsunit/es6/debug-promises-uncaught-uncaught.js
+++ b/test/mjsunit/es6/debug-promises-uncaught-uncaught.js
@@ -6,8 +6,7 @@
 
 // Test debug events when we only listen to uncaught exceptions and
 // there is a catch handler for the exception thrown in a Promise.
-// Expectation:
-//  - only the PendingExceptionInPromise debug event is triggered.
+// We expect an Exception debug event with a promise to be triggered.
 
 Debug = debug.Debug;
 
@@ -22,7 +21,7 @@ var p = new Promise(function(resolve, reject) {
 var q = p.chain(
   function() {
     log.push("throw");
-    throw new Error("uncaught");
+    throw new Error("uncaught");  // event
   });
 
 function listener(event, exec_state, event_data, data) {
@@ -31,12 +30,13 @@ function listener(event, exec_state, event_data, data) {
     if (step >= 1) return;
     assertEquals(["resolve", "end main", "throw"], log);
     if (event == Debug.DebugEvent.Exception) {
-      assertUnreachable();
-    } else if (event == Debug.DebugEvent.PendingExceptionInPromise) {
       assertEquals(0, step);
       assertEquals("uncaught", event_data.exception().message);
       assertTrue(event_data.promise() instanceof Promise);
+      assertEquals(q, event_data.promise());
       assertTrue(event_data.uncaught());
+      // Assert that the debug event is triggered at the throw site.
+      assertTrue(exec_state.frame(0).sourceLineText().indexOf("// event") > 0);
       step++;
     }
   } catch (e) {