[Cronet] Enforce implementation does not call through API classes

Such calls could fail if an older API is used that
does not contain newer methods.  Calls should instead call through a
wrapper class from VersionSafeCallbacks.

R=kapishnikov
BUG=629299

CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_cronet_tester

Review-Url: https://codereview.chromium.org/2440613003
Cr-Commit-Position: refs/heads/master@{#441186}
diff --git a/components/cronet/PRESUBMIT.py b/components/cronet/PRESUBMIT.py
index 6ab05a91..e722191e 100644
--- a/components/cronet/PRESUBMIT.py
+++ b/components/cronet/PRESUBMIT.py
@@ -71,15 +71,25 @@
     return []
 
 
+def _RunUnittests(input_api, output_api):
+  return input_api.canned_checks.RunUnitTestsInDirectory(
+      input_api, output_api, '.', [ r'^.+_unittest\.py$'])
+
+
 def CheckChangeOnUpload(input_api, output_api):
   results = []
   results.extend(_PyLintChecks(input_api, output_api))
   results.extend(
       input_api.canned_checks.CheckPatchFormatted(input_api, output_api))
   results.extend(_PackageChecks(input_api, output_api))
+  results.extend(_RunUnittests(input_api, output_api))
   return results
 
 
+def CheckChangeOnCommit(input_api, output_api):
+  return _RunUnittests(input_api, output_api)
+
+
 def _GetTryMasters(project, change):
   return {
     'master.tryserver.chromium.android': {