Make GrGLShaderBuilder::fragmentPosition() return a vec4, with 1.0 as the zw components when in the y-flip case. This works around an Adreno driver bug.

Revert "Stop referencing gl_FragCoord z and w components."

This reverts commit 160a52ba217012ed73c240f6d67b3bbf2b4879d6.

R=jvanverth@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/354663002
6 files changed