Revert "[ChromeDriver] Disabling GPU for Mac platform"

This reverts commit c7f6f0de.

Reason for revert: Reverting because it was not the root causing the issue. Test in Waterfall still fails.


Original change's description:
> [ChromeDriver] Disabling GPU for Mac platform
> 
> The waterfall tests on Mac appear to be flaky so disabling GPU for Mac platforms as well.
> 
> Bug: chromedriver:1695
> Change-Id: Id39fea14a40857bec33e78ffe2d3c65e51ada91c
> Reviewed-on: https://chromium-review.googlesource.com/884303
> Commit-Queue: Artur Khachatryan <khachatryan@chromium.org>
> Reviewed-by: John Chen <johnchen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#531669}

TBR=johnchen@chromium.org,khachatryan@chromium.org

Change-Id: Ie149de38211f1a424b5dd341f14081b30b51e61e
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromedriver:1695
Reviewed-on: https://chromium-review.googlesource.com/887168Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Artur Khachatryan <khachatryan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531985}

chrome/test/chromedriver/client/chromedriver.py

@@ -152,8 +152,7 @@ class ChromeDriver(object):
     elif chrome_binary:
       options['binary'] = chrome_binary
 
-    if (sys.platform.startswith('linux') or sys.platform.startswith('darwin')) \
-        and android_package is None:
+    if sys.platform.startswith('linux') and android_package is None:
       if chrome_switches is None:
         chrome_switches = []
       # Workaround for crbug.com/611886.