Bug 1512286 - Use the env var on non-QR platforms. r=kats

Depends on D13963

Differential Revision: https://phabricator.services.mozilla.com/D13964

--HG--
extra : moz-landing-system : lando

taskcluster/taskgraph/transforms/tests.py

@@ -955,6 +955,9 @@ def enable_webrender(config, tests):
         if test.get('webrender'):
             test['mozharness'].setdefault('extra-options', [])\
                               .append("--enable-webrender")
+        else:
+            test['mozharness'].setdefault('extra-options', [])\
+                              .append("--disable-webrender")
 
         yield test
 

testing/mozharness/scripts/awsy_script.py

@@ -51,6 +51,12 @@ class AWSY(TestingMixin, MercurialScript, TooltoolMixin, CodeCoverageMixin):
           "default": False,
           "help": "Tries to enable the WebRender compositor.",
           }],
+        [["--disable-webrender"],
+         {"action": "store_true",
+          "dest": "disable_webrender",
+          "default": False,
+          "help": "Force-disables the WebRender compositor.",
+          }],
         [["--base"],
          {"action": "store_true",
           "dest": "test_about_blank",
@@ -232,6 +238,11 @@ class AWSY(TestingMixin, MercurialScript, TooltoolMixin, CodeCoverageMixin):
             env['MOZ_WEBRENDER'] = '1'
             env['MOZ_ACCELERATED'] = '1'
 
+        # Allow explicitly disabling webrender, so that we don't run WR on non-QR
+        # test platforms just because they run on qualified hardware.
+        if self.config['disable_webrender']:
+            env['MOZ_WEBRENDER'] = '0'
+
         env['MOZ_UPLOAD_DIR'] = dirs['abs_blob_upload_dir']
         if not os.path.isdir(env['MOZ_UPLOAD_DIR']):
             self.mkdir_p(env['MOZ_UPLOAD_DIR'])