//testing/scripts: Add missing returns

It appears that some return statements were accidentally omitted during
an earlier refactor. This CL adds a few of them back.

Bug: 896175
Change-Id: I218d8ae6fa347fea775d606b5aa04064662ff7e6
Reviewed-on: https://chromium-review.googlesource.com/c/1291787Reviewed-by: Ned Nguyen <nednguyen@google.com>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Stephen Martinis <martiniss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601276}

testing/scripts/run_chromedriver_tests.py

@@ -49,7 +49,7 @@ class ChromeDriverAdapter(common.BaseIsolatedScriptArgsAdapter):
 
 def main():
   adapter = ChromeDriverAdapter()
-  adapter.run_test()
+  return adapter.run_test()
 
 
 # This is not really a "script test" so does not need to manually add

testing/scripts/run_isolated_script_test.py

@@ -80,7 +80,7 @@ class TypUnittestAdapter(common.BaseIsolatedScriptArgsAdapter):
 
   def run_test(self):
     try:
-      super(TypUnittestAdapter, self).run_test()
+      return super(TypUnittestAdapter, self).run_test()
     finally:
       # Clean up the temp filter file at the end after the test has
       # finished the run if needed.