Clarify frame rate as frames per second

Bug: 137287430
Test: n/a
Change-Id: Icf1ad4c5b9551d3690af2329290d5cc30c8016b0
diff --git a/include/android/surface_control.h b/include/android/surface_control.h
index 157b424..eeb8330 100644
--- a/include/android/surface_control.h
+++ b/include/android/surface_control.h
@@ -419,11 +419,11 @@
  * callback timings, and changes to the time interval at which the system releases buffers back to
  * the application.
  *
- * |frameRate| is the intended frame rate of this surface. 0 is a special value that indicates the
- * app will accept the system's choice for the display frame rate, which is the default behavior if
- * this function isn't called. The frameRate param does *not* need to be a valid refresh rate for
- * this device's display - e.g., it's fine to pass 30fps to a device that can only run the display
- * at 60fps.
+ * |frameRate| is the intended frame rate of this surface, in frames per second. 0 is a special
+ * value that indicates the app will accept the system's choice for the display frame rate, which is
+ * the default behavior if this function isn't called. The frameRate param does *not* need to be a
+ * valid refresh rate for this device's display - e.g., it's fine to pass 30fps to a device that can
+ * only run the display at 60fps.
  *
  * Available since API level 30.
  */