Revert "Clear atlas textures at creation in Chrome"

Revert "Clear atlas textures at creation in Chrome"

This reverts commit 8785df15fe5a57651597d138d3c5aea0ffe3f661.

Reason for revert: Chrome bug
Bug: chromium:726226

Original change's description:
> Clear atlas textures at creation in Chrome
>
> Bug: chromium:656320
> Change-Id: Ia65274aa733f199be188579821e745920493aefc
> Reviewed-on: https://skia-review.googlesource.com/17824
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> Commit-Queue: Brian Salomon <bsalomon@google.com>
>

TBR=bsalomon@google.com,robertphillips@google.com
Bug: chromium:656320

No-Tree-Checks: true
No-Try: true
No-Presubmit: true
Change-Id: Ibc4dd7f184866b58481f2dc7e7e88da9169e7adc
Reviewed-On: https://skia-review.googlesource.com/17988
Reviewed-By: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-on: https://skia-review.googlesource.com/17991