Revert "Re-enable GPU Rasterization for content with any author defined viewport."

This reverts commit a017b667a53b3ee5f8bc630be98c37ebf53a2339.

BUG=624645,591179

Appears to be causing larger performance regressions than anticipated,
reverting on release branch until this can be investigated.

Cr-Commit-Position: refs/branch-heads/2785@{#128}
Cr-Branched-From: 68623971be0cfc492a2cb0427d7f478e7b214c24-refs/heads/master@{#403382}
4 files changed