Remove legacy SwiftShader expectations in cc tests

All platforms now use SwANGLE for these tests, so we can remove the
logic and expectations for legacy SwiftShader GL.

Bug: chromium:1061151
Change-Id: I12603170c74619a54e0ae074ad9d462ccaf52237
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3453177
Reviewed-by: Kyle Charbonneau <kylechar@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Alexis Hétu <sugoi@google.com>
Cr-Commit-Position: refs/heads/main@{#969672}

cc/test/layer_tree_test.cc

@@ -996,10 +996,6 @@ void LayerTreeTest::RealEndTest() {
   base::RunLoop::QuitCurrentWhenIdleDeprecated();
 }
 
-bool LayerTreeTest::use_swangle() const {
-  return gl::GetGLImplementationParts() == gl::GetSoftwareGLImplementation();
-}
-
 void LayerTreeTest::DispatchAddNoDamageAnimation(
     Animation* animation_to_receive_animation,
     double animation_duration) {

cc/test/layer_tree_test.h

@@ -231,7 +231,6 @@ class LayerTreeTest : public testing::Test, public TestHooks {
     return false;
 #endif
   }
-  bool use_swangle() const;
 
   const viz::RendererType renderer_type_;
 

cc/trees/layer_tree_host_pixeltest_filters.cc

@@ -618,11 +618,7 @@ TEST_P(LayerTreeHostFiltersPixelTest, ImageFilterScaled) {
 
   RunPixelTest(
       background,
-      base::FilePath(
-          (use_swangle() || use_skia_vulkan())
-              ? FILE_PATH_LITERAL("backdrop_filter_on_scaled_layer_.png")
-              : FILE_PATH_LITERAL(
-                    "backdrop_filter_on_scaled_layer_legacy_swiftshader_.png"))
+      base::FilePath(FILE_PATH_LITERAL("backdrop_filter_on_scaled_layer_.png"))
           .InsertBeforeExtensionASCII(GetRendererSuffix()));
 }
 
@@ -737,11 +733,7 @@ TEST_P(LayerTreeHostFiltersPixelTest, ImageRenderSurfaceScaled) {
 
   RunPixelTest(
       background,
-      base::FilePath(
-          (use_swangle() || use_skia_vulkan())
-              ? FILE_PATH_LITERAL("scaled_render_surface_layer_.png")
-              : FILE_PATH_LITERAL(
-                    "scaled_render_surface_layer_legacy_swiftshader_.png"))
+      base::FilePath(FILE_PATH_LITERAL("scaled_render_surface_layer_.png"))
           .InsertBeforeExtensionASCII(GetRendererSuffix()));
 }
 

cc/trees/layer_tree_host_pixeltest_scrollbars.cc

@@ -175,22 +175,12 @@ TEST_P(LayerTreeHostScrollbarsPixelTest, MAYBE_HugeTransformScale) {
   scale_transform.Scale(scale, scale);
   layer->SetTransform(scale_transform);
 
-  if (use_swangle() || use_skia_vulkan() ||
-      renderer_type_ == viz::RendererType::kSkiaGL ||
-      renderer_type_ == viz::RendererType::kSkiaDawn)
-    pixel_comparator_ = std::make_unique<FuzzyPixelOffByOneComparator>(true);
+  pixel_comparator_ = std::make_unique<FuzzyPixelOffByOneComparator>(true);
 
-  RunPixelTest(
-      background,
-      base::FilePath(
-          use_swangle()
-              ? (use_skia_vulkan() ? FILE_PATH_LITERAL("spiral_64_scale_vk.png")
-                                   : FILE_PATH_LITERAL("spiral_64_scale.png"))
-              : (use_skia_vulkan()
-                     ? FILE_PATH_LITERAL(
-                           "spiral_64_scale_legacy_swiftshader_vk.png")
-                     : FILE_PATH_LITERAL(
-                           "spiral_64_scale_legacy_swiftshader.png"))));
+  RunPixelTest(background,
+               base::FilePath(use_skia_vulkan()
+                                  ? FILE_PATH_LITERAL("spiral_64_scale_vk.png")
+                                  : FILE_PATH_LITERAL("spiral_64_scale.png")));
 }
 
 class LayerTreeHostOverlayScrollbarsPixelTest