Increment CSSSegmentedFontFaceCache version when removing FontFaceRule

This prevents old font data (before the style change) from being used.

BUG=305885
TEST=no test, this code path is not used yet

Review URL: https://codereview.chromium.org/85053002

git-svn-id: svn://svn.chromium.org/blink/trunk@162598 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add Shadow DOM-related tests to TextIteratorTest.

This patch adds a few unit tests to TextIteratorTest, each of which tests
TextIterator's behavior on shadow trees.

This patch does not touch TextIterator's implementation. This change just adds
tests to capture the current behavior.

BUG=244955

Review URL: https://codereview.chromium.org/79083004

git-svn-id: svn://svn.chromium.org/blink/trunk@162599 bbb929c8-8fbe-4397-9dbb-9b2b20218538