Use HeapProfiler::FindObjectById when searching for node

v8::HeapGraphNode::GetHeapValue is going to be deprecated soon. This change switches heap profiler implementation in Blink to FindObjectById which doesn't depend on a particular heap snapshot.

BUG=324769

Review URL: https://codereview.chromium.org/104313002

git-svn-id: svn://svn.chromium.org/blink/trunk@164224 bbb929c8-8fbe-4397-9dbb-9b2b20218538