VectorComparer should check null

This is:
  https://codereview.chromium.org/332113002
Add methods for obtaining the C runtime heap handle
Merge branch 'feature/blpwtk2' into release/candidate
Merge version 36.0.1985.143_bb2

This update works around an assertion failure that happens in Debug builds, and
also adds methods for obtaining handles to the C runtime heaps.