Add next_version_mini_installer to MiniInstallerTest's compile targets.

scripts/slave/recipe_modules/chromium_tests/steps.py

Index: scripts/slave/recipe_modules/chromium_tests/steps.py
diff --git a/scripts/slave/recipe_modules/chromium_tests/steps.py b/scripts/slave/recipe_modules/chromium_tests/steps.py
index c2115f577bb6563f0c8f54913a37e7526a2a51df..3e55c4186348c49ea67187f583439ecf8c3f3cc8 100644
--- a/scripts/slave/recipe_modules/chromium_tests/steps.py
+++ b/scripts/slave/recipe_modules/chromium_tests/steps.py
@@ -1643,7 +1643,7 @@ class MiniInstallerTest(PythonBasedTest):  # pylint: disable=W0232
 
   @staticmethod
   def compile_targets(_):
-    return ['mini_installer']
+    return ['mini_installer', 'next_version_mini_installer']

[Dirk Pranke, 2016/07/26 18:47:51]

Didn't we try this once before? You can't change this like this, because the
official builders will pull this version of the recipe, and try to build
next_version_mini_installer on a branch, where the target doesn't (yet?) exist.

Or does the target now exist on all of our branches?

[fdoray, 2016/07/26 19:00:59]

Target was added before the M52 branch
https://chromium.googlesource.com/chromium/src/+/fb048bff9ec1ecdb632386878c33...
IIUC, the fact that M52 was promoted to stable means that the target now exists
on all supported branches (M51 is no longer supported).

 
   def run_step(self, api, suffix, cmd_args, **kwargs):
     test_path = api.path['checkout'].join('chrome', 'test', 'mini_installer')