Reland text autosizing changes.

This relands the following changes:
http://crrev.com/208393008 Preserve autosizing multiplier on style recalc.
http://crrev.com/209853007 Fix line height when changing multiplier.
http://crrev.com/209353003 Clean up handling of autosizing state changes.

These changes were reverted in http://crrev.com/212163006, because the first
one broke AwSettingsTest.testLayoutAlgorithmWithTwoViews.

They are safe to reland due to the fix in http://crrev.com/215063004.

BUG=353309

Review URL: https://codereview.chromium.org/215503003

git-svn-id: svn://svn.chromium.org/blink/trunk@170471 bbb929c8-8fbe-4397-9dbb-9b2b20218538