Do not draw opacity:0 backdrop-filters in software renderer

In the case that the element with backdrop-filter also has
opacity set to zero, there is no need to perform the backdrop
filtering operation. This also avoids degradation of the painted
output when backdrop_filter_quality is < 1 and opacity is 0,
as in crbug.com/1002225.

Bug: 1002225
Change-Id: I8334f6cc46f18eeda412cab7b885b1612c0315a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1833925
Commit-Queue: vmpstr <vmpstr@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Auto-Submit: Mason Freed <masonfreed@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702023}

components/viz/service/display/software_renderer.cc

@@ -649,9 +649,12 @@ void SoftwareRenderer::GenerateMipmap() {
 }
 
 bool SoftwareRenderer::ShouldApplyBackdropFilters(
-    const cc::FilterOperations* backdrop_filters) const {
+    const cc::FilterOperations* backdrop_filters,
+    const RenderPassDrawQuad* quad) const {
   if (!backdrop_filters)
     return false;
+  if (quad->shared_quad_state->opacity == 0.f)
+    return false;
   DCHECK(!backdrop_filters->IsEmpty());
   return true;
 }
@@ -755,7 +758,7 @@ sk_sp<SkShader> SoftwareRenderer::GetBackdropFilterShader(
     SkTileMode content_tile_mode) const {
   const cc::FilterOperations* backdrop_filters =
       BackdropFiltersForPass(quad->render_pass_id);
-  if (!ShouldApplyBackdropFilters(backdrop_filters))
+  if (!ShouldApplyBackdropFilters(backdrop_filters, quad))
     return nullptr;
   base::Optional<gfx::RRectF> backdrop_filter_bounds_input =
       BackdropFilterBoundsForPass(quad->render_pass_id);

components/viz/service/display/software_renderer.h

@@ -79,8 +79,8 @@ class VIZ_SERVICE_EXPORT SoftwareRenderer : public DirectRenderer {
   void DrawTextureQuad(const TextureDrawQuad* quad);
   void DrawTileQuad(const TileDrawQuad* quad);
   void DrawUnsupportedQuad(const DrawQuad* quad);
-  bool ShouldApplyBackdropFilters(
-      const cc::FilterOperations* backdrop_filters) const;
+  bool ShouldApplyBackdropFilters(const cc::FilterOperations* backdrop_filters,
+                                  const RenderPassDrawQuad* quad) const;
   sk_sp<SkImage> ApplyImageFilter(SkImageFilter* filter,
                                   const RenderPassDrawQuad* quad,
                                   const SkBitmap& to_filter,