Use GrMockContext (rather than NullGL interface) in blink unit tests

Skia's NullGL interface is deprecated, and this is the last piece of
code to use it. The Mock context is actually maintained (and simpler),
but is functionally a different backend.

With https://skia-review.googlesource.com/c/skia/+/204221, it supports
exporting textures as "GL", enough to allow CanvasResourceProvider to
work properly in tests. That, plus adding BGRA support (done here) gets
everything passing.

Change-Id: Id39101ed45f72e2294af9093e4610699936528ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1542239Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Auto-Submit: Brian Osman <brianosman@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Cr-Commit-Position: refs/heads/master@{#646299}

third_party/blink/renderer/platform/graphics/test/fake_web_graphics_context_3d_provider.h

@@ -14,7 +14,7 @@
 #include "third_party/blink/public/platform/web_graphics_context_3d_provider.h"
 #include "third_party/skia/include/core/SkRefCnt.h"
 #include "third_party/skia/include/gpu/GrContext.h"
-#include "third_party/skia/include/gpu/gl/GrGLInterface.h"
+#include "third_party/skia/include/gpu/mock/GrMockTypes.h"
 
 namespace blink {
 
@@ -24,8 +24,10 @@ class FakeWebGraphicsContext3DProvider : public WebGraphicsContext3DProvider {
                                    cc::ImageDecodeCache* cache = nullptr)
       : gl_(gl),
         image_decode_cache_(cache ? cache : &stub_image_decode_cache_) {
-    sk_sp<const GrGLInterface> gl_interface(GrGLCreateNullInterface());
-    gr_context_ = GrContext::MakeGL(std::move(gl_interface));
+    GrMockOptions mockOptions;
+    mockOptions.fConfigOptions[kBGRA_8888_GrPixelConfig] =
+        mockOptions.fConfigOptions[kRGBA_8888_GrPixelConfig];
+    gr_context_ = GrContext::MakeMock(&mockOptions);
     // enable all gpu features.
     for (unsigned feature = 0; feature < gpu::NUMBER_OF_GPU_FEATURE_TYPES;
          ++feature) {