Calculate the max possible preview frame rate for a session and attach
it to CameraSessionStats for consumption by CameraServiceProxy.

Bug: 209669709
Test: Verified values received by the CameraServiceProxy are reasonable.
Change-Id: I865ebda1cb6cbbb5769ace85a0feef8fbd84e554
diff --git a/services/camera/libcameraservice/device3/Camera3Device.h b/services/camera/libcameraservice/device3/Camera3Device.h
index 453ac3a..e926b5b 100644
--- a/services/camera/libcameraservice/device3/Camera3Device.h
+++ b/services/camera/libcameraservice/device3/Camera3Device.h
@@ -294,6 +294,8 @@
     status_t disconnectImpl();
     static status_t removeFwkOnlyRegionKeys(CameraMetadata *request);
 
+    float getMaxPreviewFps(sp<camera3::Camera3OutputStreamInterface> stream);
+
     static const size_t        kDumpLockAttempts  = 10;
     static const size_t        kDumpSleepDuration = 100000; // 0.10 sec
     static const nsecs_t       kActiveTimeout     = 500000000;  // 500 ms