Allow stepping into Object.observe handlers.

test/mjsunit/es6/debug-stepin-microtasks.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --allow-natives-syntax --expose-debug-as debug
 
 Debug = debug.Debug
 var exception = null;
 var break_count = 0;
-var expected_breaks = 7;
+var expected_breaks = -1;
 
 function listener(event, exec_state, event_data, data) {
   try {
     if (event == Debug.DebugEvent.Break) {
       assertTrue(exec_state.frameCount() != 0, "FAIL: Empty stack trace");
+      if (!break_count) {
+        // Count number of expected breakpoints in this source file.
+        var source_text = exec_state.frame(0).func().script().source();
+        expected_breaks = source_text.match(/\/\/\s*Break\s+\d+\./g).length;
+        print("Expected breaks: " + expected_breaks);
+      }
       var source = exec_state.frame(0).sourceLineText();
       print("paused at: " + source);
       assertTrue(source.indexOf("// Break " + break_count + ".") > 0,
-                 "Unexpected pause at: " + source);
+                 "Unexpected pause at: " + source + "\n" +
+                 "Expected: // Break " + break_count + ".");
       if (source.indexOf("StepOver.") !== -1) {
         exec_state.prepareStep(Debug.StepAction.StepNext, 1);
       } else {
         exec_state.prepareStep(Debug.StepAction.StepIn, 1);
       }
       ++break_count;
-    } else if (event == Debug.DebugEvent.AsyncTaskEvent &&
-               event_data.type() === "willHandle" &&
-               event_data.name() !== "Object.observe" &&
-               break_count > 0) {
-      exec_state.prepareStep(Debug.StepAction.StepIn, 1);
     }
   } catch (e) {
     exception = e;
     print(e, e.stack);
   }
 };
 
 Debug.setListener(listener);
 
 Promise.resolve(42)
   .then(promise1)
   .then(Object) // Should skip stepping into native.
   .then(Boolean) // Should skip stepping into native.
   .then(promise2)
-  .then(undefined, promise3)
+  .catch(promise3)
   .catch(function(e) {
     %AbortJS("FAIL: uncaught exception " + e);
   });
 
-function promise1()
-{
+function promise1() {
   debugger; // Break 0.
   return exception || 1; // Break 1.
 } // Break 2.
 
-function promise2()
-{
+function promise2() {
   throw new Error; // Break 3.
 }
 
-function promise3()
-{
-  finalize(); // Break 4. StepOver.
+function promise3() {
+  installObservers(); // Break 4. StepOver.
   return break_count; // Break 5.
 } // Break 6.
 
-function finalize()
-{
+function installObservers() {
+  var dummy = {};
+  Object.observe(dummy, observer1);
+  Object.observe(dummy, Object); // Should skip stepping into native.
+  Object.observe(dummy, Boolean); // Should skip stepping into native.
+  Object.observe(dummy, observer2);
+  dummy.foo = 1;
+}
+
+function observer1() {
+  return exception || 3; // Break 7.
+} // Break 8.
+
+function observer2() {
+  Promise.resolve().then(promise4); // Break 9. StepOver.
+  return break_count + 1; // Break 10.
+} // Break 11.
+
+function promise4() {
+  finalize(); // Break 12. StepOver.
+  return 0; // Break 13.
+} // Break 14. StepOver.
+
+function finalize() {
   var dummy = {};
   Object.observe(dummy, function() {
     if (expected_breaks !== break_count) {
       %AbortJS("FAIL: expected <" + expected_breaks + "> breaks instead of <" +
                break_count + ">");
     }
     if (exception !== null) {
       %AbortJS("FAIL: exception: " + exception);
     }
   });
   dummy.foo = 1;
 }