Revert "Run policy-presubmit when presubmit is changed"

This reverts commit 139c1efd.

Reason for revert: https://crbug.com/1047721

Original change's description:
> Run policy-presubmit when presubmit is changed
> 
> When policy templates are changed, syntax_check_policy_template_json.py is run as part of the presubmit checks. It should also be run when changes to the file itself were made.
> 
> Bug: 1045930
> Change-Id: Ic8870bd748d80d87b99b93889640cf2ebbbf0b27
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2022794
> Reviewed-by: Alexander Hendrich <hendrich@chromium.org>
> Commit-Queue: Anina Koehler <aninak@google.com>
> Cr-Commit-Position: refs/heads/master@{#737240}

TBR=hendrich@chromium.org,aninak@google.com

Change-Id: I9b1e9c6fc799516a5a7944706032ad5fc9cffd6f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1045930, 1047721
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2031110Reviewed-by: Alexander Hendrich <hendrich@chromium.org>
Commit-Queue: Alexander Hendrich <hendrich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737543}

components/policy/resources/PRESUBMIT.py

@@ -23,55 +23,58 @@ def _GetPolicyTemplates(template_path):
 def _CheckPolicyTemplatesSyntax(input_api, output_api):
   local_path = input_api.PresubmitLocalPath()
   filepath = input_api.os_path.join(local_path, 'policy_templates.json')
-
-  try:
-    template_affected_file = next(iter(f \
-      for f in input_api.change.AffectedFiles() \
-      if f.AbsoluteLocalPath() == filepath))
-  except:
-    template_affected_file = None
-
-  old_sys_path = sys.path
-  try:
-    tools_path = input_api.os_path.normpath(
-        input_api.os_path.join(local_path, input_api.os_path.pardir, 'tools'))
-    sys.path = [ tools_path ] + sys.path
-    # Optimization: only load this when it's needed.
-    import syntax_check_policy_template_json
-    device_policy_proto_path = input_api.os_path.join(
-        local_path, '../proto/chrome_device_policy.proto')
-    args = ["--device_policy_proto_path=" + device_policy_proto_path]
-
-    root = input_api.change.RepositoryRoot()
-
-    current_version = None
-    original_file_contents = None
-
-    # Check if there is a tag that allows us to bypass compatibility checks.
-    # This can be used in situations where there is a bug in the validation
-    # code or if a policy change needs to urgently be submitted.
-    if not input_api.change.tags.get('BYPASS_POLICY_COMPATIBILITY_CHECK'):
-      # Get the current version from the VERSION file so that we can check
-      # which policies are un-released and thus can be changed at will.
-      try:
-        version_path = input_api.os_path.join(root, 'chrome', 'VERSION')
-        with open(version_path, "rb") as f:
-          current_version = int(f.readline().split("=")[1])
-          print ('Checking policies against current version: ' +
-            current_version)
-      except:
-        pass
-
-      # Get the original file contents of the policy file so that we can check
-      # the compatibility of template changes in it
-      if template_affected_file is not None:
-        original_file_contents = '\n'.join(template_affected_file.OldContents())
-
-    checker = syntax_check_policy_template_json.PolicyTemplateChecker()
-    if checker.Run(args, filepath, original_file_contents, current_version) > 0:
-      return [output_api.PresubmitError('Syntax error(s) in file:', [filepath])]
-  finally:
-    sys.path = old_sys_path
+  if any(f.AbsoluteLocalPath() == filepath
+         for f in input_api.AffectedFiles()):
+    old_sys_path = sys.path
+    try:
+      tools_path = input_api.os_path.normpath(
+          input_api.os_path.join(local_path, input_api.os_path.pardir, 'tools'))
+      sys.path = [ tools_path ] + sys.path
+      # Optimization: only load this when it's needed.
+      import syntax_check_policy_template_json
+      device_policy_proto_path = input_api.os_path.join(
+          local_path, '../proto/chrome_device_policy.proto')
+      args = ["--device_policy_proto_path=" + device_policy_proto_path]
+
+      root = input_api.change.RepositoryRoot()
+
+      current_version = None
+      original_file_contents = None
+
+      # Check if there is a tag that allows us to bypass compatibility checks.
+      # This can be used in situations where there is a bug in the validation
+      # code or if a policy change needs to urgently be submitted.
+      if not input_api.change.tags.get('BYPASS_POLICY_COMPATIBILITY_CHECK'):
+        # Get the current version from the VERSION file so that we can check
+        # which policies are un-released and thus can be changed at will.
+        try:
+          version_path = input_api.os_path.join(
+          root, 'chrome', 'VERSION')
+          with open(version_path, "rb") as f:
+            current_version = int(f.readline().split("=")[1])
+            print ('Checking policies against current version: ' +
+              current_version)
+        except:
+          pass
+
+        # Get the original file contents of the policy file so that we can check
+        # the compatibility of template changes in it
+        template_path = input_api.os_path.join(
+          root, 'components', 'policy', 'resources', 'policy_templates.json')
+        affected_files = input_api.change.AffectedFiles()
+        template_affected_file = next(iter(f \
+          for f in affected_files if f.AbsoluteLocalPath() == template_path))
+        if template_affected_file is not None:
+          original_file_contents = \
+            '\n'.join(template_affected_file.OldContents())
+
+      checker = syntax_check_policy_template_json.PolicyTemplateChecker()
+      if checker.Run(args, filepath,
+        original_file_contents, current_version) > 0:
+        return [output_api.PresubmitError('Syntax error(s) in file:',
+                                          [filepath])]
+    finally:
+      sys.path = old_sys_path
   return []
 
 
@@ -207,14 +210,11 @@ def _CheckMissingPlaceholders(input_api, output_api, template_path):
 def _CommonChecks(input_api, output_api):
   results = []
   root = input_api.change.RepositoryRoot()
-  template_path = input_api.os_path.join(
+  template_path = template_path = input_api.os_path.join(
       root, 'components', 'policy', 'resources', 'policy_templates.json')
   # policies in chrome/test/data/policy/policy_test_cases.json.
   test_cases_path = input_api.os_path.join(
       root, 'chrome', 'test', 'data', 'policy', 'policy_test_cases.json')
-  syntax_check_path = input_api.os_path.join(
-      root, 'components', 'policy', 'tools',
-      'syntax_check_policy_template_json.py')
   affected_files = input_api.change.AffectedFiles()
 
   results.extend(_CheckMissingPlaceholders(input_api, output_api,
@@ -223,17 +223,15 @@ def _CommonChecks(input_api, output_api):
     for f in affected_files)
   tests_changed = any(f.AbsoluteLocalPath() == test_cases_path \
     for f in affected_files)
-  syntax_check_changed = any(f.AbsoluteLocalPath() == syntax_check_path \
-    for f in affected_files)
 
-  if template_changed or tests_changed or syntax_check_changed:
+  if template_changed or tests_changed:
     try:
       policies = _GetPolicyTemplates(template_path)
     except:
       results.append(output_api.PresubmitError('Invalid Python/JSON syntax.'))
       return results
     results.extend(_CheckPolicyTestCases(input_api, output_api, policies))
-    if template_changed or syntax_check_changed:
+    if template_changed:
       results.extend(_CheckPolicyTemplatesSyntax(input_api, output_api))
       results.extend(_CheckPolicyHistograms(input_api, output_api, policies))