Fix NarrowingCompoundAssignment warning

This ErrorProne warning was enabled in
http://crrev.com/96c7ab0153ae97a8d8e05949f36cd7bb8eedbf1d
https://webrtc-review.googlesource.com/60849

Bug: None
Change-Id: I5e622f84925ee96e7743d2c08d17fcdb4c4a0f55
Reviewed-on: https://webrtc-review.googlesource.com/60940
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Commit-Queue: Oleh Prypin <oprypin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22362}
diff --git a/sdk/android/api/org/webrtc/VideoFileRenderer.java b/sdk/android/api/org/webrtc/VideoFileRenderer.java
index 995c562..1b9fa48 100644
--- a/sdk/android/api/org/webrtc/VideoFileRenderer.java
+++ b/sdk/android/api/org/webrtc/VideoFileRenderer.java
@@ -101,9 +101,9 @@
     int cropWidth = buffer.getWidth();
     int cropHeight = buffer.getHeight();
     if (fileAspectRatio > frameAspectRatio) {
-      cropHeight *= frameAspectRatio / fileAspectRatio;
+      cropHeight = (int) (cropHeight * (frameAspectRatio / fileAspectRatio));
     } else {
-      cropWidth *= fileAspectRatio / frameAspectRatio;
+      cropWidth = (int) (cropWidth * (fileAspectRatio / frameAspectRatio));
     }
 
     final int cropX = (buffer.getWidth() - cropWidth) / 2;