message: Enable RenderPassLoadOpTests on Vulkan back-ends
  RenderPassLoadOpTests can pass on Vulkan back-ends now.
diff: @@ -165,4 +165,4 @@ TEST_P(RenderPassLoadOpTests, ColorClearThenLoadAndDraw) {
  EXPECT_TEXTURE_RGBA8_EQ(expectBlue.data(), renderTarget, kRTSize / 2, 0, kRTSize / 2, kRTSize, 0);
  }
  -DAWN_INSTANTIATE_TEST(RenderPassLoadOpTests, D3D12Backend, MetalBackend, OpenGLBackend)
  +DAWN_INSTANTIATE_TEST(RenderPassLoadOpTests, D3D12Backend, MetalBackend, OpenGLBackend, VulkanBackend)
  