Add a pure virtual method to the GarbageCollectedMixin class

Source/modules/screen_orientation/ScreenOrientationDispatcher.h

Index: Source/modules/screen_orientation/ScreenOrientationDispatcher.h
diff --git a/Source/modules/screen_orientation/ScreenOrientationDispatcher.h b/Source/modules/screen_orientation/ScreenOrientationDispatcher.h
index 5cf0f38e7f06575e25603a8c8d1f16c3014bed26..bb3fb209e6f6feee19794ffdd1f0df2e9c2a75d8 100644
--- a/Source/modules/screen_orientation/ScreenOrientationDispatcher.h
+++ b/Source/modules/screen_orientation/ScreenOrientationDispatcher.h
@@ -19,6 +19,7 @@ namespace blink {
 // ScreenOrientationDispatcher is listening, that means that the platform should
 // be polling if required.
 class ScreenOrientationDispatcher final : public GarbageCollectedFinalized<ScreenOrientationDispatcher>, public PlatformEventDispatcher {
+    USING_GARBAGE_COLLECTED_MIXIN(ScreenOrientationDispatcher);
 public:
     static ScreenOrientationDispatcher& instance();