Web Inspector: HeapProfiler: upstream retainedSize calculation.

Web Inspector: HeapProfiler: upstream retainedSize calculation.
https://bugs.webkit.org/show_bug.cgi?id=87107

This patch upstreams V8::HeapSnapshotGenerator::CalculateRetainedSizes function to front-end.
After that we will be able to drop retainedSize field from the snapshot serialized data.
See meta-bug https://bugs.webkit.org/show_bug.cgi?id=87089

Reviewed by Yury Semikhatsky.

PerformanceTests:

* inspector/heap-snapshot.html: add counter for the _calculateRetainedSize method.

Source/WebCore:

* inspector/front-end/HeapSnapshot.js:
(WebInspector.HeapSnapshotNode.prototype.get retainedSize):
(WebInspector.HeapSnapshot.prototype._init):
(WebInspector.HeapSnapshot.prototype._calculateRetainedSizes):

LayoutTests:

* inspector/profiler/heap-snapshot-expected.txt:
* inspector/profiler/heap-snapshot.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@117953 268f45cc-cd09-0410-ab3c-d52691b4dbfc