Invert DSF to map from delegated frame to layer space

cc/layers/delegated_renderer_layer_impl.cc

Index: cc/layers/delegated_renderer_layer_impl.cc
diff --git a/cc/layers/delegated_renderer_layer_impl.cc b/cc/layers/delegated_renderer_layer_impl.cc
index f59e1f2c1da785613c631d44f316f7a555519c35..29e1b06441c66a62fd3e0e0091b5efa4b0ba15a9 100644
--- a/cc/layers/delegated_renderer_layer_impl.cc
+++ b/cc/layers/delegated_renderer_layer_impl.cc
@@ -146,8 +146,8 @@ void DelegatedRendererLayerImpl::SetFrameData(
   // the frame, so intersect the damage to the layer's bounds.
   RenderPass* new_root_pass = render_pass_list.back();
   gfx::Size frame_size = new_root_pass->output_rect.size();
-  gfx::RectF damage_in_layer = MathUtil::MapClippedRect(
-      DelegatedFrameToLayerSpaceTransform(frame_size), damage_in_frame);
+  gfx::RectF damage_in_layer = damage_in_frame;
+  damage_in_layer.Scale(1.0 / layer_tree_impl()->device_scale_factor());
   SetUpdateRect(gfx::IntersectRects(
       gfx::UnionRects(update_rect(), damage_in_layer), gfx::Rect(bounds())));
 
@@ -196,17 +196,6 @@ void DelegatedRendererLayerImpl::ReleaseResources() {
   ClearChildId();
 }
 
-gfx::Transform DelegatedRendererLayerImpl::DelegatedFrameToLayerSpaceTransform(
-    const gfx::Size& frame_size) const {
-  gfx::Size display_size = display_size_.IsEmpty() ? bounds() : display_size_;
-
-  gfx::Transform delegated_frame_to_layer_space_transform;
-  delegated_frame_to_layer_space_transform.Scale(
-      static_cast<double>(display_size.width()) / frame_size.width(),
-      static_cast<double>(display_size.height()) / frame_size.height());
-  return delegated_frame_to_layer_space_transform;
-}
-
 static inline int IndexToId(int index) { return index + 1; }
 static inline int IdToIndex(int id) { return id - 1; }
 
@@ -242,9 +231,11 @@ void DelegatedRendererLayerImpl::AppendContributingRenderPasses(
   const RenderPass* root_delegated_render_pass =
       render_passes_in_draw_order_.back();
   gfx::Size frame_size = root_delegated_render_pass->output_rect.size();
-  gfx::Transform delegated_frame_to_root_transform =
-      screen_space_transform() *
-      DelegatedFrameToLayerSpaceTransform(frame_size);
+  gfx::Transform delegated_frame_to_root_transform = screen_space_transform();
+  double inverse_device_scale_factor =
+      1.0 / layer_tree_impl()->device_scale_factor();
+  delegated_frame_to_root_transform.Scale(inverse_device_scale_factor,
+                                          inverse_device_scale_factor);
 
   for (size_t i = 0; i < render_passes_in_draw_order_.size() - 1; ++i) {
     RenderPass::Id output_render_pass_id(-1, -1);
@@ -416,8 +407,11 @@ void DelegatedRendererLayerImpl::AppendRenderPassQuads(
         // Don't allow areas inside the bounds that are empty.
         DCHECK(display_size_.IsEmpty() ||
                gfx::Rect(display_size_).Contains(gfx::Rect(bounds())));
-        gfx::Transform delegated_frame_to_target_transform =
-            draw_transform() * DelegatedFrameToLayerSpaceTransform(frame_size);
+        gfx::Transform delegated_frame_to_target_transform = draw_transform();
+        double inverse_device_scale_factor =
+            1.0 / layer_tree_impl()->device_scale_factor();
+        delegated_frame_to_target_transform.Scale(inverse_device_scale_factor,
+                                                  inverse_device_scale_factor);
 
         output_shared_quad_state->content_to_target_transform.ConcatTransform(
             delegated_frame_to_target_transform);