Avoid SLOW_ASSERT when calling HeapGraphNode::GetChildrenCount

Avoid SLOW_ASSERT when calling HeapGraphNode::GetChildrenCount

It may occur that GetChildrenCount is called on the node which has no children and stored last in the internal nodes array. In that case HeapEntry::children_arr() would fail when taking address of the element at index children_index_ which is past the last element in the children's array.

BUG=None
LOG=N
R=alph@chromium.org, ulan@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=18378

[yurys, 2013-12-18 13:39:55]

This change fixes test failure found in
https://codereview.chromium.org/117483002/

[ulan, 2013-12-18 13:42:50]

LGTM, thank you for fixing it!

[alph, 2013-12-18 13:46:58]

lgtm

https://codereview.chromium.org/112623005/diff/1/src/heap-snapshot-generator-...
File src/heap-snapshot-generator-inl.h (right):

https://codereview.chromium.org/112623005/diff/1/src/heap-snapshot-generator-...
src/heap-snapshot-generator-inl.h:62: SLOW_ASSERT(children_index_ <=
snapshot_->children().length());
SLOW_ASSERT(children_index_ < snapshot_->children().length() ||
            children_index_ == snapshot_->children().length() && children_count_
== 0)

[yurys, 2013-12-18 15:07:15]

https://codereview.chromium.org/112623005/diff/1/src/heap-snapshot-generator-...
File src/heap-snapshot-generator-inl.h (right):

https://codereview.chromium.org/112623005/diff/1/src/heap-snapshot-generator-...
src/heap-snapshot-generator-inl.h:62: SLOW_ASSERT(children_index_ <=
snapshot_->children().length());
On 2013/12/18 13:46:59, alph wrote:
> SLOW_ASSERT(children_index_ < snapshot_->children().length() ||
>             children_index_ == snapshot_->children().length() &&
children_count_
> == 0)

Done.

[alph, 2013-12-18 15:15:50]

https://codereview.chromium.org/112623005/diff/20001/src/heap-snapshot-genera...
File src/heap-snapshot-generator-inl.h (right):

https://codereview.chromium.org/112623005/diff/20001/src/heap-snapshot-genera...
src/heap-snapshot-generator-inl.h:65: return &snapshot_->children().first() +
children_index_;
first -> start

[yurys, 2013-12-18 15:19:27]

https://codereview.chromium.org/112623005/diff/20001/src/heap-snapshot-genera...
File src/heap-snapshot-generator-inl.h (right):

https://codereview.chromium.org/112623005/diff/20001/src/heap-snapshot-genera...
src/heap-snapshot-generator-inl.h:65: return &snapshot_->children().first() +
children_index_;
On 2013/12/18 15:15:51, alph wrote:
> first -> start

List doesn't have start(), you may have confused it with Vector::start().

[yurys, 2013-12-20 07:33:30]

Committed patchset #2 manually as r18378 (presubmit successful).