Web Inspector: Auto expand retaining path until there are more than one retainer.
https://bugs.webkit.org/show_bug.cgi?id=112596

Patch by Alexei Filippov <alph@chromium.org> on 2013-03-28
Reviewed by Yury Semikhatsky.

Source/WebCore:

When retainers view gets opened automatically expand retaining path
for objects having just a single retainer.

Test: inspector/profiler/heap-snapshot-summary-retainers.html

* inspector/front-end/HeapSnapshotDataGrids.js:
(WebInspector.HeapSnapshotRetainmentDataGrid.prototype.populateComplete):
(WebInspector.HeapSnapshotRetainmentDataGrid.prototype.setDataSource):
* inspector/front-end/HeapSnapshotGridNodes.js:
(WebInspector.HeapSnapshotGridNode.prototype.childrenRetrieved):
(WebInspector.HeapSnapshotGridNode.prototype._populateChildren):

LayoutTests:

When retainers view gets opened automatically expand retaining path
for objects having just a single retainer.
- Added a test for the new behavior.
- Replaced hardcoded "populate complete" string with the event object.

* inspector/profiler/heap-snapshot-summary-retainers-expected.txt:
* inspector/profiler/heap-snapshot-summary-retainers.html:
* inspector/profiler/heap-snapshot-test.js:
(initialize_HeapSnapshotTest.):
(initialize_HeapSnapshotTest):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147090 268f45cc-cd09-0410-ab3c-d52691b4dbfc