Bug 1499208 - Use task name to determine gpu-ness of backfilled tasks; r=jmaher

Existing mozharness per_test_base logic determines gpu-ness in the same way: If the
requested test is in a manifest for a suite named 'reftest', '*gpu', or 'webgl*',
then the test should only be run in a gpu-enabled test-verify and will be skipped
otherwise. With this change, backfill will select between TV/TVg based on the
name of the originating task, applying the same rule. So, to backfill a test in TV,
select the backfill action from a non-gpu task; to backfill a test in TVg, select
the backfill action from a gpu task.

taskcluster/taskgraph/actions/backfill.py

@@ -118,17 +118,14 @@ def backfill_action(parameters, graph_config, input, task_group_id, task_id, tas
                     task.task['extra']['treeherder']['symbol'] += '-p'
 
                 if input.get('testPath', ''):
-                    tp = input.get('testPath', '')
                     is_wpttest = 'web-platform' in task.task['metadata']['name']
                     is_android = 'android' in task.task['metadata']['name']
                     gpu_required = False
-                    # TODO: this has a high chance of getting out of date
                     if (not is_wpttest) and \
                        ('gpu' in task.task['metadata']['name'] or
                         'webgl' in task.task['metadata']['name'] or
-                        'canvas' in tp or
-                        'gfx/tests' in tp or
-                        ('reftest' in tp and 'jsreftest' not in tp)):
+                        ('reftest' in task.task['metadata']['name'] and
+                         'jsreftest' not in task.task['metadata']['name'])):
                         gpu_required = True
 
                     # Create new cmd that runs a test-verify type job