Ensure that the drag view is not dimmed.

- When picking up a task view to dock it, we should animate remove the
  dim on the task view so that when you drop it, there is no jump from
  the dimmed version to non-dimmed app.

Bug: 27154882
Change-Id: Ifa1493227593dd950e49650b69f178cef82bc82e

packages/SystemUI/src/com/android/systemui/recents/views/TaskStackView.java

@@ -1765,6 +1765,7 @@ public class TaskStackView extends FrameLayout implements TaskStack.TaskStackCal
                 mTmpTransform, null);
         mTmpTransform.scale = finalScale;
         mTmpTransform.translationZ = mLayoutAlgorithm.mMaxTranslationZ + 1;
+        mTmpTransform.dimAlpha = 0f;
         updateTaskViewToTransform(event.taskView, mTmpTransform,
                 new AnimationProps(DRAG_SCALE_DURATION, Interpolators.FAST_OUT_SLOW_IN));
     }