Merge pull request #1970 from robintown/firefox-visual-glitches

Fix a couple of visual glitches on Firefox

src/room/InCallView.module.css

@@ -28,7 +28,9 @@ limitations under the License.
   flex-direction: column;
   overflow: auto;
   overflow-inline: hidden;
-  contain: strict;
+  /* There used to be a contain: strict here, but due to some bugs in Firefox,
+  this was causing the Z-ordering of modals to glitch out. It can be added back
+  if those issues appear to be resolved. */
 }
 
 .centerMessage {

src/video-grid/VideoTile.module.css

@@ -38,6 +38,10 @@ limitations under the License.
   height: 100%;
   object-fit: cover;
   background-color: var(--cpd-color-bg-subtle-primary);
+  /* This transform is a no-op, but it forces Firefox to use a different
+  rendering path, one that actually clips the corners of <video> elements into
+  the intended rounded shape. We can remove this if Firefox stops being broken. */
+  transform: translate(0);
 }
 
 .videoTile.isLocal:not(.screenshare) video {