Revert "Added SkSL workaround for devices which cannot safely access gl_FragCoord"

This reverts commit 1001f843a45e95f6df1d44242b6b06c77898e870.

Reason for revert: Many failures.

Original change's description:
> Added SkSL workaround for devices which cannot safely access gl_FragCoord
> 
> This is the root cause of https://github.com/flutter/flutter/issues/13216
> I've got a GM that demonstrates the bug, but only in Viewer.
> 
> Bug: skia:7410
> Change-Id: Iaa1f27b10166aa09e4dc5949e5a6ca1bd14c99ac
> Reviewed-on: https://skia-review.googlesource.com/93920
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>

TBR=bsalomon@google.com,brianosman@google.com,ethannicholas@google.com

Change-Id: I2a2edc0a8fa11fe9dac1045dc79ae91106518b02
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:7410
Reviewed-on: https://skia-review.googlesource.com/94281
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
6 files changed