Web Inspector: serialize edge counts instead of indexes in heap snapshot

Web Inspector: serialize edge counts instead of indexes in heap snapshot
https://bugs.webkit.org/show_bug.cgi?id=88324

The serialized node structure currently holds an index
of its first containment edge in the edges array.
The index can be quite big (up to 7 digits for large snapshots).
The patch changes the serialization format to pass
node containment edge count instead. For most nodes the count
is just a single digit number.
This reduces serialized snapshot size and therefore its transfer time.

Patch by Alexei Filippov <alexeif@chromium.org> on 2012-06-05
Reviewed by Yury Semikhatsky.

PerformanceTests:

* inspector/heap-snapshot-performance-test.js:

Source/WebCore:

* inspector/front-end/HeapSnapshot.js:
(WebInspector.HeapSnapshotNode.prototype._edgeIndexesStart):
(WebInspector.HeapSnapshotNode.prototype._edgeIndexesEnd):
(WebInspector.HeapSnapshotNode.prototype._ordinal):
(WebInspector.HeapSnapshotNodeIterator):
(WebInspector.HeapSnapshot.prototype._init):
(WebInspector.HeapSnapshot.prototype._buildEdgeIndexes):
(WebInspector.HeapSnapshot.prototype._buildRetainers):
(WebInspector.HeapSnapshot.prototype._bfs):
(WebInspector.HeapSnapshot.prototype._buildAggregates):
(WebInspector.HeapSnapshot.prototype._buildPostOrderIndex):
(WebInspector.HeapSnapshot.prototype._buildDominatorTree):
(WebInspector.HeapSnapshot.prototype._markPageOwnedNodes):
(WebInspector.HeapSnapshot.prototype._markQueriableHeapObjects):

LayoutTests:

* inspector/profiler/heap-snapshot-expected.txt:
* inspector/profiler/heap-snapshot-test.js:
(initialize_HeapSnapshotTest.InspectorTest.createHeapSnapshotMockObject):
(initialize_HeapSnapshotTest.InspectorTest.createHeapSnapshotMockRaw):
(initialize_HeapSnapshotTest.InspectorTest.createHeapSnapshotMockWithDOM):
(initialize_HeapSnapshotTest.):
* inspector/profiler/heap-snapshot.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@119498 268f45cc-cd09-0410-ab3c-d52691b4dbfc