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Previously we invalidated only new recorded pixels on tiles that
resized but ignored new recording tiles. The problem with this is that
if the old layer size is on the boundary of recording tiles, then we
invalidate nothing. But there may be raster tiles that would like to
use the new recording tiles, and currently have uninitialized content
in them, but they don't get invalidated to hear about it.

R=vmpstr
BUG=411774

Review URL: https://codereview.chromium.org/556973003

Cr-Commit-Position: refs/heads/master@{#294203}