Revert "Update documentation for DISPLAY_DECORATION"

Revert "Add/plumb SurfaceControl.DISPLAY_DECORATION"

Revert "Add eLayerIsDisplayDecoration flag"

Revert submission 16511727-wm_DISPLAY_DECORATION

Reason for revert: b/211835607
Reverted Changes:
I1da3199ba:Allow changing composition from DISPLAY_DECORATION...
I1fae74b36:Update documentation for DISPLAY_DECORATION
I1da03a88f:Add eLayerIsDisplayDecoration flag
I7f22dfd03:Add/plumb SurfaceControl.DISPLAY_DECORATION

Change-Id: I7238bcc96325873ec7dbdd42894192c48e7cf92e
diff --git a/graphics/composer/aidl/android/hardware/graphics/composer3/Composition.aidl b/graphics/composer/aidl/android/hardware/graphics/composer3/Composition.aidl
index 49cdffc..4947463 100644
--- a/graphics/composer/aidl/android/hardware/graphics/composer3/Composition.aidl
+++ b/graphics/composer/aidl/android/hardware/graphics/composer3/Composition.aidl
@@ -74,20 +74,16 @@
      */
     SIDEBAND = 5,
     /**
-     * A display decoration layer contains a buffer which is used to provide
+     * A display decoration layer contains a buffer which is an 8 bit
+     * alpha mask. Pixels in the mask with an alpha of 0 (transparent) will
+     * show the content underneath, and pixels with an alpha of 255 will be
+     * be rendered in black. An alpha in between will show the content
+     * blended with black. This is useful, for example, to provide
      * anti-aliasing on the cutout region/rounded corners on the top and
      * bottom of a display.
      *
-     * Pixels in the buffer with an alpha of 0 (transparent) will show the
-     * content underneath, and pixels with an alpha of 255 will be rendered in
-     * black. An alpha in between will show the underlying content blended with
-     * black.
-     *
-     * Some devices may support this flag with a buffer containing an 8 bit
-     * alpha mask.
-     *
      * Upon validateDisplay, the device may request a change from this type
-     * to either DEVICE or CLIENT.
+     * to CLIENT.
      */
     DISPLAY_DECORATION = 6,
 }