Bug 1719232 - Simplify check for empty valid rect. r=jrmuizel

We know from testing that the device valid rect itself can sometimes
be empty which produces the symptom that the compositor valid rect
is empty after quantization to i32. So it is sufficient to just check
if that device rect is empty, rather than having to use get_surface_rect
to reproduce the math downstream that produces the compositor valid
rect.

Differential Revision: https://phabricator.services.mozilla.com/D121453

gfx/wr/webrender/src/picture.rs

@@ -546,9 +546,6 @@ struct TilePostUpdateContext<'a> {
     /// If true, the scale factor of the root transform for this picture
     /// cache changed, so we need to invalidate the tile and re-render.
     invalidate_all: bool,
-
-    /// Index of the compositor transform mapping local -> device pixels.
-    transform_index: CompositorTransformIndex,
 }
 
 // Mutable state passed to picture cache tiles during post_update
@@ -1232,16 +1229,10 @@ impl Tile {
         // Invalidate the tile based on the content changing.
         self.update_content_validity(ctx, state, frame_context);
 
-        // Bug 1719232 - The valid rect once converted to i32 does not describe
-        // a non-empty region. Cull the tile as a workaround.
-        let compositor_valid_rect = state.composite_state.get_surface_rect(
-            &self.current_descriptor.local_valid_rect,
-            &self.local_tile_rect,
-            ctx.transform_index,
-        ).to_i32();
-
         // If there are no primitives there is no need to draw or cache it.
-        if self.current_descriptor.prims.is_empty() || compositor_valid_rect.is_empty() {
+        // Bug 1719232 - The final device valid rect does not always describe a non-empty
+        // region. Cull the tile as a workaround.
+        if self.current_descriptor.prims.is_empty() || self.device_valid_rect.is_empty() {
             // If there is a native compositor surface allocated for this (now empty) tile
             // it must be freed here, otherwise the stale tile with previous contents will
             // be composited. If the tile subsequently gets new primitives added to it, the
@@ -3930,7 +3921,6 @@ impl TileCacheInstance {
             local_rect: self.local_rect,
             z_id: ZBufferId::invalid(),
             invalidate_all: self.invalidate_all_tiles,
-            transform_index: self.transform_index,
         };
 
         let mut state = TilePostUpdateState {