Fix crashes in components/policy/resources/PRESUBMIT.py.

components/policy/resources/PRESUBMIT.py

Index: components/policy/resources/PRESUBMIT.py
diff --git a/components/policy/resources/PRESUBMIT.py b/components/policy/resources/PRESUBMIT.py
index 3870875aa379667a0dc5c6d59e95347b8e3934b3..e34e1acfd49cb448154ce5c0ea6dd484fcc2cbe2 100644
--- a/components/policy/resources/PRESUBMIT.py
+++ b/components/policy/resources/PRESUBMIT.py
@@ -105,7 +105,11 @@ def _CommonChecks(input_api, output_api):
   template_path = os_path.join(local_path, 'policy_templates.json')
   affected_files = input_api.AffectedFiles()
   if any(f.AbsoluteLocalPath() == template_path for f in affected_files):
-    policies = _GetPolicyTemplates(template_path)
+    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))
     results.extend(_CheckPolicyHistograms(input_api, output_api, policies))