Don't convert invalidations to a FloatRect.

We just turn it back into an IntRect on the cc side.

Depends on: https://codereview.chromium.org/647253002/
Depends on: https://codereview.chromium.org/655863002/

R=enne
BUG=342848

Review URL: https://codereview.chromium.org/646133002

git-svn-id: svn://svn.chromium.org/blink/trunk@183693 bbb929c8-8fbe-4397-9dbb-9b2b20218538