Fix a bug in software renderer for backdrop filters

Prior to this CL, an invalid color filter would cause a renderer crash
in software_renderer. This is now fixed.

Bug: 1004054
Change-Id: I0182b1dd475d2aab909611aa9a01351863e0632d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1819960
Commit-Queue: Mason Freed <masonfreed@chromium.org>
Auto-Submit: Mason Freed <masonfreed@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699448}

cc/trees/layer_tree_host_pixeltest_filters.cc

@@ -138,6 +138,26 @@ TEST_P(LayerTreeHostFiltersPixelTest, BackdropFilterBlurRect) {
           : base::FilePath(FILE_PATH_LITERAL("backdrop_filter_blur.png")));
 }
 
+TEST_P(LayerTreeHostFiltersPixelTest, BackdropFilterInvalid) {
+  scoped_refptr<SolidColorLayer> background =
+      CreateSolidColorLayer(gfx::Rect(200, 200), SK_ColorWHITE);
+  scoped_refptr<SolidColorLayer> green =
+      CreateSolidColorLayer(gfx::Rect(50, 50, 100, 100), kCSSGreen);
+  scoped_refptr<SolidColorLayer> blur =
+      CreateSolidColorLayer(gfx::Rect(30, 30, 140, 140), SK_ColorTRANSPARENT);
+  background->AddChild(green);
+  background->AddChild(blur);
+
+  // This should be an invalid filter, and result in just the original green.
+  FilterOperations filters;
+  filters.Append(FilterOperation::CreateHueRotateFilter(9e99));
+  blur->SetBackdropFilters(filters);
+
+  RunPixelTest(
+      renderer_type(), background,
+      base::FilePath(FILE_PATH_LITERAL("backdrop_filter_invalid.png")));
+}
+
 TEST_P(LayerTreeHostFiltersPixelTest, BackdropFilterBlurRadius) {
   if (renderer_type() == RENDERER_SOFTWARE) {
     // TODO(989238): Software renderer does not support/implement

components/viz/service/display/software_renderer.cc

@@ -812,12 +812,14 @@ sk_sp<SkShader> SoftwareRenderer::GetBackdropFilterShader(
       (unclipped_rect.top_right() - backdrop_rect.top_right()) +
       (backdrop_rect.bottom_left() - unclipped_rect.bottom_left());
 
-  sk_sp<SkImageFilter> filter =
+  sk_sp<cc::PaintFilter> paint_filter =
       cc::RenderSurfaceFilters::BuildImageFilter(
           *backdrop_filters,
           gfx::SizeF(backdrop_bitmap.width(), backdrop_bitmap.height()),
-          clipping_offset)
-          ->cached_sk_filter_;
+          clipping_offset);
+  if (!paint_filter)
+    return nullptr;
+  sk_sp<SkImageFilter> filter = paint_filter->cached_sk_filter_;
 
   // TODO(989238): Software renderer does not support/implement kClamp_TileMode.
   SkIRect result_rect;