cc: Delete non-impl-side-painting animation freezing logic

cc: Delete non-impl-side-painting animation freezing logic

This deletes code that froze the animation clock when we skipped
frames because of checkerboarding. This logic was only enabled
for non-impl-side painting (to handle the case of animating very large
layers, where failing to freeze the clock would cause rasterization to
constantly lag behind, resulting in checkerboarding whenever a draw was
forced). Since all shipping renderers use impl-side painting now, this
logic is no longer needed.

BUG=None

Review URL: https://codereview.chromium.org/654203007

Cr-Commit-Position: refs/heads/master@{#300277}