Don't dereference null pointer in FastTextAutosizer::getTentativeClusterRoots()

The result of m_blocksForFingerprint.get() can be a null pointer, so don't
dereference it (that invokes undefined behaviour). Instead, just return the pointer.

Recent versions of Clang will optimize based on references always pointing
to valid objects. In the previous code below:

  BlockSet* roots = m_fingerprintMapper.getTentativeClusterRoots(fingerprint);
  if (!roots || roots->size() < 2 || !roots->contains(block))
      return 0;

the "!roots" null check would be optimized away, since "roots" is the address
of a reference, and must therefore point to a valid object.

BUG=38149
TEST=fast/text-autosizing tests don't crash with new Clang

Review URL: https://codereview.chromium.org/418253003

git-svn-id: svn://svn.chromium.org/blink/trunk@179171 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove prefixed Pointer Lock API.

The Pointer Lock API http://www.w3.org/TR/pointerlock has already been
implemented without prefix, this change removes the 'webkit' prefixed
API endpoints.

Intent to Deprecate and Remove:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/tN8fWRtG0MI

BUG=398457

Review URL: https://codereview.chromium.org/424093006

git-svn-id: svn://svn.chromium.org/blink/trunk@179172 bbb929c8-8fbe-4397-9dbb-9b2b20218538