DevTools: Make StepInto work across script boundaries and Blink process tasks.

DevTools: Make StepInto work across script boundaries and Blink process tasks.

This will make StepInto to step:
- across Blink process tasks, like setTimeout
- across js->blink->js within one Blink process (event handlers, custom events)
- across inlined <script> tags

BUG=432468
R=vsevik, yurys, pfeldman

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185530

[aandrey, 2014-11-14 14:02:53]

Coming next:
- across V8 microtasks (promises and O.o)

[aandrey, 2014-11-18 11:53:53]

ping?

[yurys, 2014-11-18 12:35:26]

I think it would make sense to pause in the beginning of the next task if we are
stepping-over. WDYT?

https://codereview.chromium.org/732593002/diff/40001/LayoutTests/inspector/so...
File
LayoutTests/inspector/sources/debugger/debugger-step-into-across-timeouts.html
(right):

https://codereview.chromium.org/732593002/diff/40001/LayoutTests/inspector/so...
LayoutTests/inspector/sources/debugger/debugger-step-into-across-timeouts.html:21:
(function FAIL_Should_Not_Pause_Here() { debugger; })();
Why do we need this code?

https://codereview.chromium.org/732593002/diff/40001/Source/core/inspector/In...
File Source/core/inspector/InspectorDOMDebuggerAgent.cpp (left):

https://codereview.chromium.org/732593002/diff/40001/Source/core/inspector/In...
Source/core/inspector/InspectorDOMDebuggerAgent.cpp:152: if (m_debuggerAgent &&
m_debuggerAgent->runningNestedMessageLoop())
Now we can remove runningNestedMessageLoop from the debugger agent and script
debug server.

[aandrey, 2014-11-18 13:35:01]

On 2014/11/18 12:35:26, yurys wrote:
> I think it would make sense to pause in the beginning of the next task if we
are
> stepping-over. WDYT?

I think, pausing on StepOver/StepOut would be confusing, and in some cases
totally wrong. E.g. when stepping on "element.dispatchEvent(new CustomEvent())"
we should step into the event listener only on StepInto, since this is a
synchronous js->blink->js call.

Moreover, before we used to step across event listeners and custom element
callbacks via StepInto only.

With the async debugging scenario I think we should "promote" only StepInto.
StepOut seems a bad candidate for this, and StepOver may be confusing.

For example,
If we assume that setTimeout callbacks are called synchronously, stepping with
StepOver would never get you from one callback to the next one, right? Thus, I
think it's confusing to promote StepOver in async world.

While the example above is artificial, for example, the Object.observe()
delivery does call its callbacks synchronously within one microtask.

https://codereview.chromium.org/732593002/diff/40001/LayoutTests/inspector/so...
File
LayoutTests/inspector/sources/debugger/debugger-step-into-across-timeouts.html
(right):

https://codereview.chromium.org/732593002/diff/40001/LayoutTests/inspector/so...
LayoutTests/inspector/sources/debugger/debugger-step-into-across-timeouts.html:21:
(function FAIL_Should_Not_Pause_Here() { debugger; })();
On 2014/11/18 12:35:25, yurys wrote:
> Why do we need this code?

To make it *fail* w/o this patch instead of timing out.

[yurys, 2014-11-18 14:12:16]

lgtm

[aandrey, 2014-11-18 14:20:46]

The CQ bit was checked by aandrey@chromium.org

[vsevik, 2014-11-18 14:21:34]

> I think, pausing on StepOver/StepOut would be confusing, and in some cases
> totally wrong. E.g. when stepping on "element.dispatchEvent(new
CustomEvent())"
> we should step into the event listener only on StepInto, since this is a
> synchronous js->blink->js call.

I think we still should pause in the next task after stepping over the last
statement in current task.
Am I missing something?

[commit-bot: I haz the power, 2014-11-18 14:21:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/732593002/60001

[vsevik, 2014-11-18 14:23:23]

The CQ bit was unchecked by vsevik@chromium.org

[aandrey, 2014-11-18 15:41:57]

The CQ bit was checked by aandrey@chromium.org

[commit-bot: I haz the power, 2014-11-18 15:42:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/732593002/60001

[commit-bot: I haz the power, 2014-11-18 15:44:46]

Committed patchset #4 (id:60001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=185530