Reset SquashingState's boundingRect for new CLM

This makes updateSquashingStateForNewMapping clear
SquashingState's boundingRect for the new mapping,
rather than retaining the previous mapping's boundingRect.

BUG=None

Review URL: https://codereview.chromium.org/286233003

git-svn-id: svn://svn.chromium.org/blink/trunk@174122 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Only set title on SVG documents

Only set title on SVG documents, HTML document should not be affected.

Review URL: https://codereview.chromium.org/291483003

git-svn-id: svn://svn.chromium.org/blink/trunk@174123 bbb929c8-8fbe-4397-9dbb-9b2b20218538