Allow unit tests to force serial execution in the test launcher.

Allow unit tests to force serial execution in the test launcher.

Test case names that begin with "SERIALIZE_" are now always executed
serially by the test launcher. When the new test launcher was initially
enabled, the clipboard tests were moved to interactive_ui_tests because
they require serial execution, due to the global nature of the
clipboard. However, this meant that they never ran on Android, since
Android has no interactive_ui_tests target.

BUG=434620
R=phajdan.jr@chromium.org,thakis@chromium.org

[dcheng, 2015-03-21 13:37:13]

The main objection I see is that marking tests for serial execution differs a
little from PRE_ marking.

e.g.

SERIALIZE_TestCase.TestName

instead of

TestCase.PRE_TestName

To be perfectly honest, I chose this approach because it was slightly less work
for me in clipboard_test_template.h, but it's easy enough to make it match PRE_.
WDYT?

[dcheng, 2015-03-21 13:37:33]

(also, assuming this patch is OK, I plan on handling
clipboard_android_unittest.cc in a followup patch)

[Paweł Hajdan Jr., 2015-03-23 13:28:57]

I'm open to changing the test launcher to allow this.

Could you just start an email thread on chromium-dev and infra-dev to ask what
other people think? A potential issue with adding a new test prefix is that it's
sort of like API and it's hard to remove once more and more tests start
depending on it.

[dcheng, 2015-03-24 08:17:41]

So I sketched out what implementing jam@'s suggestion of hiding the SERIALIZE_
prefix might look like. Since this gets a bit involved, I wanted to get some
opinions before spending more time pursuing this.

In short, the places that pass around test names would change to use
base::TestID. This would have simple accessors for getting test name, the pretty
name for printing, as well as the original name to pass to the actual test
runner. Internally, it has the logic for stripping away test prefixes/reporting
them to interested parties.

If we do this, I think we'd want to do it for both DISABLED_and SERIALIZE(D)_.
It'd be a bit weird to do it for one but not the other. But I'm not sure if this
would result in more confusion--the set of tests that the runner executes
wouldn't look the same as the set of tests listed in the code. Thoughts?