[inspector] fixed crash on attempt to access empty scope_info on break

[inspector] fixed crash on attempt to access empty scope_info on break

Nested arrow functions could have empty scope_info, we need to ensure its creation.

BUG=chromium:696202
R=yangguo@chromium.org

[kozy, 2017-02-27 22:26:24]

Description was changed from

==========
[inspector] fixed crash on attempt to access to empty scope_info on break

Nested arrow functions could have empty scope_info, we need to ensure its
creation.

BUG=chromium:696202
R=yangguo@chromium.org
==========

to

==========
[inspector] fixed crash on attempt to access empty scope_info on break

Nested arrow functions could have empty scope_info, we need to ensure its
creation.

BUG=chromium:696202
R=yangguo@chromium.org
==========

[kozy, 2017-02-27 22:29:05]

Yang, please take a look!

I think that root of issue is skipping scope without allocated variables of
nested arrow function in Scope::AllocateDebuggerScopeInfos. Check in this
function should not assume that function_scope always has scope_info.

[Yang, 2017-02-28 12:43:12]

yangguo@chromium.org changed reviewers:
+ verwaest@chromium.org

[Yang, 2017-02-28 12:43:13]

LGTM. Toon, could you give this a look?

[Toon Verwaest, 2017-02-28 14:19:58]

This doesn't seem like the correct fix to me. Scope info allocation for the
debugger should only happen for a single function at a time. There's probably
something going wrong with scope info allocation of the arrow function when we
step into it? 

I think the current fix will still fail if the arrow function we step into is a
sibling rather than nested?

[Yang, 2017-03-14 12:16:43]

On 2017/02/28 14:19:58, Toon Verwaest wrote:
> This doesn't seem like the correct fix to me. Scope info allocation for the
> debugger should only happen for a single function at a time. There's probably
> something going wrong with scope info allocation of the arrow function when we
> step into it? 
> 
> I think the current fix will still fail if the arrow function we step into is
a
> sibling rather than nested?

The correct fix is here: https://codereview.chromium.org/2751573003#