Make _CheckUniquePtr an upload-only check

Currently, _CheckUniquePtr is run both on upload and on commit. This
check emits errors, which means commit is blocked if it fires. At the
same time, it has a history of false positives (one mentioned in
https://crrev.com/c/933547, another in https://crbug.com/827961).

Therefore this CL makes _CheckUniquePtr an upload-only check.

Bug: 827961
Change-Id: I6d5a7f3dda33432ae1375359c2ae573e5ad3df34
Reviewed-on: https://chromium-review.googlesource.com/990133Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Vaclav Brozek <vabr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548760}

PRESUBMIT.py

@@ -2768,7 +2768,6 @@ def _CommonChecks(input_api, output_api):
           source_file_filter=lambda x: x.LocalPath().endswith('.grd')))
   results.extend(_CheckSpamLogging(input_api, output_api))
   results.extend(_CheckForAnonymousVariables(input_api, output_api))
-  results.extend(_CheckUniquePtr(input_api, output_api))
   results.extend(_CheckUserActionUpdate(input_api, output_api))
   results.extend(_CheckNoDeprecatedCss(input_api, output_api))
   results.extend(_CheckNoDeprecatedJs(input_api, output_api))
@@ -3168,6 +3167,7 @@ def CheckChangeOnUpload(input_api, output_api):
   results.extend(_CheckSyslogUseWarning(input_api, output_api))
   results.extend(_CheckGoogleSupportAnswerUrl(input_api, output_api))
   results.extend(_CheckCrbugLinksHaveHttps(input_api, output_api))
+  results.extend(_CheckUniquePtr(input_api, output_api))
   return results