Don't use SkBlendMode::kSrc when quads are opaque in SkiaRenderer.

If quads are antialiased this can trigger shader blending.

Also Skia has optimized code paths for textures drawn src-over.

Bug: 811523
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel
Change-Id: I9f0405d7651464aeb761c02f5d16f4de29dbbd75
Reviewed-on: https://chromium-review.googlesource.com/c/1259543Reviewed-by: weiliangc <weiliangc@chromium.org>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Cr-Commit-Position: refs/heads/master@{#596363}

components/viz/service/display/skia_renderer.cc

@@ -493,14 +493,9 @@ void SkiaRenderer::DoDrawQuad(const DrawQuad* quad,
     current_paint_.setFilterQuality(kLow_SkFilterQuality);
   }
 
-  if (quad->ShouldDrawWithBlending() ||
-      quad->shared_quad_state->blend_mode != SkBlendMode::kSrcOver) {
-    current_paint_.setAlpha(quad->shared_quad_state->opacity * 255);
-    current_paint_.setBlendMode(
-        static_cast<SkBlendMode>(quad->shared_quad_state->blend_mode));
-  } else {
-    current_paint_.setBlendMode(SkBlendMode::kSrc);
-  }
+  current_paint_.setAlpha(quad->shared_quad_state->opacity * 255);
+  current_paint_.setBlendMode(
+      static_cast<SkBlendMode>(quad->shared_quad_state->blend_mode));
 
   if (draw_region) {
     gfx::QuadF local_draw_region(*draw_region);