Add camera focus distances API.

Applications can use this API to estimate the distance
between the subject and the camera.

bug:1955650
Change-Id: Ie6c8ea4971759cab6c9bcdda2c5ceb5925791c27
diff --git a/libs/camera/CameraParameters.cpp b/libs/camera/CameraParameters.cpp
index cfb7ba1..035fa9f 100644
--- a/libs/camera/CameraParameters.cpp
+++ b/libs/camera/CameraParameters.cpp
@@ -69,8 +69,10 @@
 const char CameraParameters::KEY_ZOOM_RATIOS[] = "zoom-ratios";
 const char CameraParameters::KEY_ZOOM_SUPPORTED[] = "zoom-supported";
 const char CameraParameters::KEY_SMOOTH_ZOOM_SUPPORTED[] = "smooth-zoom-supported";
+const char CameraParameters::KEY_FOCUS_DISTANCES[] = "focus-distances";
 
 const char CameraParameters::TRUE[] = "true";
+const char CameraParameters::INFINITY[] = "Infinity";
 
 // Values for white balance settings.
 const char CameraParameters::WHITE_BALANCE_AUTO[] = "auto";