Make debugger step into bound callbacks passed to Array.forEach.

BUG=chromium:450004
R=yangguo@chromium.org, kozyatinskiy@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/1030673002

Cr-Commit-Position: refs/heads/master@{#27419}

src/runtime/runtime-debug.cc

@@ -2738,7 +2738,7 @@ RUNTIME_FUNCTION(Runtime_GetScript) {
 }
 
 
-// Check whether debugger and is about to step into the callback that is passed
+// Check whether debugger is about to step into the callback that is passed
 // to a built-in function such as Array.forEach.
 RUNTIME_FUNCTION(Runtime_DebugCallbackSupportsStepping) {
   DCHECK(args.length() == 1);
@@ -2748,9 +2748,12 @@ RUNTIME_FUNCTION(Runtime_DebugCallbackSupportsStepping) {
     return isolate->heap()->false_value();
   }
   CONVERT_ARG_CHECKED(Object, callback, 0);
-  // We do not step into the callback if it's a builtin or not even a function.
-  return isolate->heap()->ToBoolean(callback->IsJSFunction() &&
-                                    !JSFunction::cast(callback)->IsBuiltin());
+  // We do not step into the callback if it's a builtin other than a bound,
+  // or not even a function.
+  return isolate->heap()->ToBoolean(
+      callback->IsJSFunction() &&
+      (!JSFunction::cast(callback)->IsBuiltin() ||
+       JSFunction::cast(callback)->shared()->bound()));
 }
 
 
@@ -2775,7 +2778,7 @@ RUNTIME_FUNCTION(Runtime_DebugPrepareStepInIfStepping) {
   // if we do not leave the builtin.  To be able to step into the function
   // again, we need to clear the step out at this point.
   debug->ClearStepOut();
-  debug->FloodWithOneShot(fun);
+  debug->FloodWithOneShotGeneric(fun);
   return isolate->heap()->undefined_value();
 }
 

test/mjsunit/debug-stepin-foreach.js

@@ -37,15 +37,17 @@ function listener(event, exec_state, event_data, data) {
 };
 
 Debug.setListener(listener);
+var bound_callback = callback.bind(null);
 
 debugger; // Break 0.
 [1,2].forEach(callback); // Break 1.
+[3,4].forEach(bound_callback); // Break 6.
 
 function callback(x) {
-  return x; // Break 2. // Break 4.
-} // Break 3. // Break 5.
+  return x; // Break 2. // Break 4. // Break 7. // Break 9.
+} // Break 3. // Break 5. // Break 8. // Break 10.
 
-assertNull(exception); // Break 6.
+assertNull(exception); // Break 11.
 assertEquals(expected_breaks, break_count);
 
 Debug.setListener(null);

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

@@ -0,0 +1,65 @@
+// Copyright 2015 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: --expose-debug-as debug --allow-natives-syntax --noalways-opt
+// Tests stepping into through Promises.
+
+Debug = debug.Debug
+var exception = null;
+var break_count = 0;
+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 + "\n" +
+                 "Expected: // Break " + break_count + ".");
+      ++break_count;
+      if (break_count !== expected_breaks) {
+        exec_state.prepareStep(Debug.StepAction.StepIn, 1);
+      }
+    }
+  } catch(e) {
+    exception = e;
+    print(e, e.stack);
+  }
+};
+
+Debug.setListener(listener);
+
+Promise.resolve(42)
+  .then(
+    function f0() {
+      debugger;  // Break 0.
+    } // Break 1.
+  )
+  .then(callback)
+  .then(callback.bind(null))
+  .then(Object)
+  .then(callback.bind(null).bind(null))
+  .then(finalize)
+  .catch(function(err) {
+    %AbortJS("FAIL: " + err);
+  });
+
+function callback(x) {
+  return x; // Break 2. // Break 4. // Break 6.
+} // Break 3. // Break 5. // Break 7.
+
+function finalize() {
+  assertNull(exception); // Break 8.
+  assertEquals(expected_breaks, break_count);
+
+  Debug.setListener(null);
+}