Revert "Trying out using only 1 chrome instance for PixelDiff to reduce noise"
Revert "Trying out using only 1 chrome instance for PixelDiff to reduce noise"

This reverts commit ade5b371824f803c36000897ee6d4e98b9b40dcf.

Reason for revert: Does not seem to help much

Original change's description:
> Trying out using only 1 chrome instance for PixelDiff to reduce noise
> 
> Bug: skia:
> Change-Id: I9a1f1930bee3a21225edba4c0868511c86f76734
> Reviewed-on: https://skia-review.googlesource.com/38221
> Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
> Reviewed-by: Ben Wagner <benjaminwagner@google.com>
> Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

TBR=benjaminwagner@google.com,9fa2e7438b8cb730f96b74865492597170561628@google.com

Change-Id: I8acd9bdd61cf3ac1ea8e1a694a4de4c4b9092619
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/38680
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot