Switch GPU Gold heuristic

Switches the heuristic that GPU Gold tests use to determine if they're
running on a workstation or not. Previously, it checked for the presence
of a git repository, but is now checking for the presence of the
SWARMING_SERVER environment variable. This is the heuristic that will
be used in other test types as they get switched to use Gold.

Also removes the RunInChromiumSrc context manager that was being used to
run the git commands, as it's simpler to just pass cwd to subprocess.

Change-Id: If1b2fdf2ebda355319359d80017b25e24bb07d0e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2033637Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737528}

content/test/gpu/gpu_tests/skia_gold_integration_test_base.py

@@ -2,7 +2,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import contextlib
 from datetime import date
 import json
 import logging
@@ -42,16 +41,6 @@ SKIA_GOLD_INSTANCE = 'chrome-gpu'
 SKIA_GOLD_CORPUS = SKIA_GOLD_INSTANCE
 
 
-@contextlib.contextmanager
-def RunInChromiumSrc():
-  old_cwd = os.getcwd()
-  os.chdir(path_util.GetChromiumSrcDir())
-  try:
-    yield
-  finally:
-    os.chdir(old_cwd)
-
-
 # This is mainly used to determine if we need to run a subprocess through the
 # shell - on Windows, finding executables via PATH doesn't work properly unless
 # run through the shell.
@@ -556,19 +545,16 @@ class SkiaGoldIntegrationTestBase(gpu_integration_test.GpuIntegrationTest):
     # Use the --local-run value if it's been set.
     elif cls.GetParsedCommandLineOptions().local_run is not None:
       cls._local_run = cls.GetParsedCommandLineOptions().local_run
-    # Look for the presence of a git repo as a heuristic to determine whether
-    # we're running on a workstation or a bot.
-    else:
-      with RunInChromiumSrc():
-        try:
-          subprocess.check_output(['git', 'status'], shell=IsWin())
-          logging.warning(
+    # Look for the presence of the SWARMING_SERVER environment variable as a
+    # heuristic to determine whether we're running on a workstation or a bot.
+    # This should always be set on swarming, but would be strange to be set on
+    # a workstation.
+    cls._local_run = 'SWARMING_SERVER' not in os.environ
+    if cls._local_run:
+      logging.warning(
               'Automatically determined that test is running on a workstation')
-          cls._local_run = True
-        except subprocess.CalledProcessError:
-          logging.warning(
-              'Automatically determined that test is running on a bot')
-          cls._local_run = False
+    else:
+      logging.warning('Automatically determined that test is running on a bot')
     return cls._local_run
 
   @classmethod
@@ -582,15 +568,16 @@ class SkiaGoldIntegrationTestBase(gpu_integration_test.GpuIntegrationTest):
       cls._build_revision = cls.GetParsedCommandLineOptions().build_revision
     # Try to determine what revision we're on using git.
     else:
-      with RunInChromiumSrc():
-        try:
-          cls._build_revision = subprocess.check_output(
-              ['git', 'rev-parse', 'origin/master'], shell=IsWin()).strip()
-          logging.warning('Automatically determined build revision to be %s',
-              cls._build_revision)
-        except subprocess.CalledProcessError:
-          raise Exception('--build-revision not passed, and unable to '
-                          'determine revision using git')
+      try:
+        cls._build_revision = subprocess.check_output(
+            ['git', 'rev-parse', 'origin/master'],
+            shell=IsWin(),
+            cwd=path_util.GetChromiumSrcDir()).strip()
+        logging.warning('Automatically determined build revision to be %s',
+            cls._build_revision)
+      except subprocess.CalledProcessError:
+        raise Exception('--build-revision not passed, and unable to '
+                        'determine revision using git')
     return cls._build_revision
 
   @classmethod