Merge "Camera: Clarify AF_REGIONS behavior in capture_result"

camera/ndk/include/camera/NdkCameraMetadataTags.h

@@ -651,7 +651,8 @@ typedef enum acamera_metadata_tag {
      * is used, all non-zero weights will have the same effect. A region with 0 weight is
      * ignored.</p>
      * <p>If all regions have 0 weight, then no specific metering area needs to be used by the
-     * camera device.</p>
+     * camera device. The capture result will either be a zero weight region as well, or
+     * the region selected by the camera device as the focus area of interest.</p>
      * <p>If the metering region is outside the used ACAMERA_SCALER_CROP_REGION returned in
      * capture result metadata, the camera device will ignore the sections outside the crop
      * region and output only the intersection rectangle as the metering region in the result