Bug 1384905 - Take 2 - [tc-migration] Windows 8 should not be triggered on try (unless specified) r=dustin

The first version of the patch didn't account for the fact that if we did -p all we still couldn't do -u foo[Windows 8]

specifically: -p all means self.platforms is None
https://hg.mozilla.org/mozilla-central/file/16ffc1d05422/taskcluster/taskgraph/try_option_syntax.py#l563

Then we check if the *test* has a run_on_projects that has either `all` or `try`, it doesn't so we abort.

In new code, we merely set a flag to say don't-run-me-by-default and use that in a few places.

MozReview-Commit-ID: 6rjNVZvpYGA

--HG--
extra : rebase_source : 4c791c9e566a5eddc2bb2e820bab0090f9db1237

taskcluster/taskgraph/try_option_syntax.py

@@ -558,6 +558,7 @@ class TryOptionSyntax(object):
             return set(['try', 'all']) & set(attr('run_on_projects', []))
 
         def match_test(try_spec, attr_name):
+            run_by_default = True
             if attr('build_type') not in self.build_types:
                 return False
             if self.platforms is not None:
@@ -565,9 +566,9 @@ class TryOptionSyntax(object):
                     return False
             else:
                 if not check_run_on_projects():
-                    return False
+                    run_by_default = False
             if try_spec is None:
-                return True
+                return run_by_default
             # TODO: optimize this search a bit
             for test in try_spec:
                 if attr(attr_name) == test['test']:
@@ -580,8 +581,10 @@ class TryOptionSyntax(object):
                 platform = attr('test_platform', '').split('/')[0]
                 # Platforms can be forced by syntax like "-u xpcshell[Windows 8]"
                 return platform in test['platforms']
-            else:
+            elif run_by_default:
                 return check_run_on_projects()
+            else:
+                return False
 
         job_try_name = attr('job_try_name')
         if job_try_name: