Bug 1597559 - Fix tile opacity getting out of sync with compositor surface. r=sotaro

Differential Revision: https://phabricator.services.mozilla.com/D55761

--HG--
extra : moz-landing-system : lando

gfx/wr/webrender/src/picture.rs

@@ -865,11 +865,6 @@ impl Tile {
             return false;
         }
 
-        // Check if this tile can be considered opaque.
-        let tile_is_opaque = ctx.backdrop.rect.contains_rect(&self.clipped_rect);
-        let opacity_changed = tile_is_opaque != self.is_opaque;
-        self.is_opaque = tile_is_opaque;
-
         // Invalidate the tile based on the content changing.
         self.update_content_validity(ctx, state);
 
@@ -878,6 +873,13 @@ impl Tile {
             return false;
         }
 
+        // Check if this tile can be considered opaque. Opacity state must be updated only
+        // after all early out checks have been performed. Otherwise, we might miss updating
+        // the native surface next time this tile becomes visible.
+        let tile_is_opaque = ctx.backdrop.rect.contains_rect(&self.clipped_rect);
+        let opacity_changed = tile_is_opaque != self.is_opaque;
+        self.is_opaque = tile_is_opaque;
+
         // Check if the selected composite mode supports dirty rect updates. For Draw composite
         // mode, we can always update the content with smaller dirty rects. For native composite
         // mode, we can only use dirty rects if the compositor supports partial surface updates.