Deduplicate Gold properties code

Updates the PDFiumSkiaGoldProperties implementation to no override the
_GetGitOriginMainHeadSha1 implementation since an equivalent
implementation is now the default. Instead, now only the repo's root
directory is required.

Bug: chromium:1443021
Change-Id: If502fc3fd1ba408b4c5e7139b401a69e8d118847
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/107250
Reviewed-by: K. Moon <kmoon@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

testing/tools/skia_gold/pdfium_skia_gold_properties.py

diff --git a/testing/tools/skia_gold/pdfium_skia_gold_properties.py b/testing/tools/skia_gold/pdfium_skia_gold_properties.py
index aeb8ef9..874e643 100644
--- a/testing/tools/skia_gold/pdfium_skia_gold_properties.py
+++ b/testing/tools/skia_gold/pdfium_skia_gold_properties.py
@@ -3,25 +3,12 @@
 # found in the LICENSE file.
 """PDFium implementation of //build/skia_gold_common/skia_gold_properties.py."""
 
-import subprocess
-import sys
-
 import pdfium_root
 from skia_gold_common import skia_gold_properties
 
 
 class PDFiumSkiaGoldProperties(skia_gold_properties.SkiaGoldProperties):
 
-  @staticmethod
-  def _GetGitOriginMainHeadSha1():
+  def _GetGitRepoDirectory(self):
     root_finder = pdfium_root.RootDirectoryFinder()
-    try:
-      return subprocess.check_output(['git', 'rev-parse', 'origin/main'],
-                                     shell=_IsWin(),
-                                     cwd=root_finder.pdfium_root).strip()
-    except subprocess.CalledProcessError:
-      return None
-
-
-def _IsWin():
-  return sys.platform == 'win32'
+    return root_finder.pdfium_root