Add DrawingBuffer multisample resolve unit test.

third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTestHelpers.h

Index: third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTestHelpers.h
diff --git a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTestHelpers.h b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTestHelpers.h
index fa44cfccaca1811d20865b92626bef5b463fc119..7df2a0711db98ebb1d1647583145edc481595c34 100644
--- a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTestHelpers.h
+++ b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTestHelpers.h
@@ -24,14 +24,14 @@ class DrawingBufferForTests : public DrawingBuffer {
       std::unique_ptr<WebGraphicsContext3DProvider> context_provider,
       DrawingBuffer::Client* client,
       const IntSize& size,
-      PreserveDrawingBuffer preserve) {
+      PreserveDrawingBuffer preserve,
+      bool multisample_extension_supported) {

[Justin Novosad, 2017/04/12 19:22:15]

Use an enum instead of a bool here.  It's rule #10 of the blink style guide:
https://sites.google.com/a/chromium.org/dev/blink/coding-style

     std::unique_ptr<Extensions3DUtil> extensions_util =
         Extensions3DUtil::Create(context_provider->ContextGL());
     RefPtr<DrawingBufferForTests> drawing_buffer =
         AdoptRef(new DrawingBufferForTests(std::move(context_provider),
                                            std::move(extensions_util), client,
                                            preserve));
-    bool multisample_extension_supported = false;
     if (!drawing_buffer->Initialize(size, multisample_extension_supported)) {
       drawing_buffer->BeginDestruction();
       return nullptr;