Implement ./mach check --media-stack

While at it, extract --media-stack flag into command_base.py.

python/servo/build_commands.py

@@ -155,10 +155,6 @@ class MachCommands(CommandBase):
     @CommandArgument('--jobs', '-j',
                      default=None,
                      help='Number of jobs to run in parallel')
-    @CommandArgument('--media-stack',
-                     default=None,
-                     choices=["gstreamer", "dummy"],
-                     help='Which media stack to use')
     @CommandArgument('--no-package',
                      action='store_true',
                      help='For Android, disable packaging into a .apk after building')

python/servo/command_base.py

@@ -792,6 +792,12 @@ install them, let us know by filing a bug!")
                 default=None,
                 help='Cross compile for given target platform',
             ),
+            CommandArgument(
+                '--media-stack',
+                default=None,
+                choices=["gstreamer", "dummy"],
+                help='Which media stack to use',
+            ),
             CommandArgument(
                 '--android',
                 default=None,

python/servo/devenv_commands.py

@@ -38,16 +38,34 @@ class MachCommands(CommandBase):
         'params', default=None, nargs='...',
         help="Command-line arguments to be passed through to cargo check")
     @CommandBase.build_like_command_arguments
-    def check(self, params, **kwargs):
+    def check(self, params, features=[], media_stack=None, target=None,
+              android=False, magicleap=False, **kwargs):
         if not params:
             params = []
 
+        features = features or []
+
+        target, android = self.pick_target_triple(target, android, magicleap)
+
+        # A guess about which platforms should use the gstreamer media stack
+        if not(media_stack):
+            if (
+                    not(target) or
+                    ("armv7" in target and "android" in target) or
+                    ("x86_64" in target)
+            ):
+                media_stack = "gstreamer"
+            else:
+                media_stack = "dummy"
+
+        features += ["media-" + media_stack]
+
         self.ensure_bootstrapped()
         self.ensure_clobbered()
         env = self.build_env()
 
         build_start = time()
-        status = self.run_cargo_build_like_command("check", params, env=env, **kwargs)
+        status = self.run_cargo_build_like_command("check", params, env=env, features=features, **kwargs)
         elapsed = time() - build_start
 
         notify_build_done(self.config, elapsed, status == 0)

python/servo/post_build_commands.py

@@ -238,10 +238,6 @@ class PostBuildCommands(CommandBase):
     @CommandArgument(
         'params', nargs='...',
         help="Command-line arguments to be passed through to cargo doc")
-    @CommandArgument('--media-stack',
-                     default=None,
-                     choices=["gstreamer", "dummy"],
-                     help='Which media stack to use')
     @CommandBase.build_like_command_arguments
     def doc(self, params, features, target=None, android=False, magicleap=False,
             media_stack=None, **kwargs):