Revert "Use vpython rather than python for GPU tests on the bots."

This reverts commit aad276cb.

Reason for revert: Suspected to be the culprit for breaking Mac browser_tests and unit_tests that use an local python test server, e.g.:

 RUN      ] CloudPolicyTest.FetchPolicy
[4513:779:0131/005831.599342:3098052568384:ERROR:local_test_server_posix.cc(81)] poll() timed out; bytes_read=0
[4513:779:0131/005831.599552:3098052743513:ERROR:local_test_server_posix.cc(168)] Could not read server_data_len
../../chrome/browser/policy/cloud/cloud_policy_browsertest.cc:190: Failure
Value of: test_server_->Start()
  Actual: false
Expected: true

Original change's description:
> Use vpython rather than python for GPU tests on the bots.
> 
> From talking with iannucci@, this is the easiest way to use vpython
> with these tests on the bots. Once the LUCI conversion is done, this
> will be a no-op, and can be removed.
> 
> Incorporate the newly deployed pyobjc wheels into Chromium's root
> .vpython; they are needed by helper scripts in the GPU directory.
> 
> Bug: 776804, 804174
> Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
> Change-Id: I1c720a9f7992e411aa85bcc7959de95ecc03c1f5
> Reviewed-on: https://chromium-review.googlesource.com/869512
> Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
> Commit-Queue: Kenneth Russell <kbr@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#533226}

TBR=iannucci@chromium.org,kbr@chromium.org,dnj@chromium.org,nednguyen@google.com

Change-Id: Idb03a7a1176d79443b3a29267a16c7631fbf1be8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 776804, 804174
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Reviewed-on: https://chromium-review.googlesource.com/894208Reviewed-by: Balazs Engedy <engedy@chromium.org>
Commit-Queue: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533285}

.vpython

@@ -124,19 +124,3 @@ wheel: <
   name: "infra/python/wheels/simplejson/${vpython_platform}"
   version: "version:3.13.2"
 >
-
-# Used by:
-#   content/test/gpu/gpu_tests/color_profile_manager_mac.py
-wheel: <
-  name: "infra/python/wheels/pyobjc/${vpython_platform}"
-  version: "version:4.1"
-  match_tag: < platform: "macosx_10_10_intel" >
->
-# TODO(crbug.com/804174): roll out support in vpython for
-# "not_match_tag", then uncomment this.
-# wheel: <
-#   name: "infra/python/wheels/pyobjc/${vpython_platform}"
-#   version: "version:2.5.1"
-#   match_tag: < platform: "macosx_10_6_intel" >
-#   not_match_tag: < platform: "macosx_10_10_intel" >
-# >

testing/scripts/run_gpu_integration_test_as_googletest.py

@@ -104,10 +104,7 @@ def main():
     rc = 0
     try:
       env['CHROME_HEADLESS'] = '1'
-      main_command = [sys.executable]
-      if not os.getenv('VIRTUAL_ENV'):
-        main_command = ['vpython']
-      rc = common.run_command(main_command + rest_args + sharding_args + [
+      rc = common.run_command([sys.executable] + rest_args + sharding_args + [
         '--write-full-results-to', args.isolated_script_test_output
       ], env=env)
     except Exception: