Always set damage rect to output rect if 3D context was reshaped.

cc/output/dc_layer_overlay.cc

Index: cc/output/dc_layer_overlay.cc
diff --git a/cc/output/dc_layer_overlay.cc b/cc/output/dc_layer_overlay.cc
index eda508e6e13243b6787f3c841565d0d0f0aa788c..6aff4b38ef773e4f385c82b45e7d7f67649598f0 100644
--- a/cc/output/dc_layer_overlay.cc
+++ b/cc/output/dc_layer_overlay.cc
@@ -117,13 +117,13 @@ DCLayerOverlayProcessor::DCLayerResult DCLayerOverlayProcessor::FromDrawQuad(
 }
 
 void DCLayerOverlayProcessor::Process(ResourceProvider* resource_provider,
+                                      bool was_reshaped,
                                       const gfx::RectF& display_rect,
                                       QuadList* quad_list,
                                       gfx::Rect* overlay_damage_rect,
                                       gfx::Rect* damage_rect,
                                       DCLayerOverlayList* ca_layer_overlays) {

[ccameron, 2017/05/11 08:49:17]

This function is doing both the "overlay" strategy (which is pretty simple) and
the "underlay" strategy (which is pretty subtle).

Do you think we could internally split this into two functions -- bool
ProcessForOverlays and bool ProcessForUnderlays, and have this function do
  if (ProcessForOverlays(...))
    ProcessForUnderlays(...);

   gfx::Rect this_frame_underlay_rect;
-  bool display_rect_changed = (display_rect != previous_display_rect_);
   for (auto it = quad_list->begin(); it != quad_list->end(); ++it) {
     DCLayerOverlay ca_layer;
     DCLayerResult result = FromDrawQuad(resource_provider, display_rect,
@@ -146,7 +146,7 @@ void DCLayerOverlayProcessor::Process(ResourceProvider* resource_provider,
       // underneath it.
       if (it->shared_quad_state->quad_to_target_transform
               .Preserves2dAxisAlignment() &&
-          !display_rect_changed && !it->ShouldDrawWithBlending()) {
+          !was_reshaped && !it->ShouldDrawWithBlending()) {
         damage_rect->Subtract(quad_rectangle);
       }
       quad_list->EraseAndInvalidateAllPointers(it);
@@ -175,7 +175,7 @@ void DCLayerOverlayProcessor::Process(ResourceProvider* resource_provider,
         // area for this and last frame, as that may have changed.
         if (it->shared_quad_state->quad_to_target_transform
                 .Preserves2dAxisAlignment() &&
-            !display_rect_changed) {
+            !was_reshaped) {

[ccameron, 2017/05/11 08:49:17]

Drive-by comment -- is this if missing a
  else {
    damage_rect->Union(quad_rectangle);
  }
?

           gfx::Rect occluding_damage_rect = *damage_rect;
           occluding_damage_rect.Intersect(quad_rectangle);
           damage_rect->Subtract(quad_rectangle);
@@ -201,7 +201,6 @@ void DCLayerOverlayProcessor::Process(ResourceProvider* resource_provider,
   }
   damage_rect->Intersect(gfx::ToEnclosingRect(display_rect));
   previous_frame_underlay_rect_ = this_frame_underlay_rect;
-  previous_display_rect_ = display_rect;
 }
 
 }  // namespace cc