message: Initialize BlendDescriptor with default values.
  TEST=dawn_end2end_tests
diff: @@ -29,8 +29,10 @@ namespace dawn_native {
  struct BlendInfo {
  bool blendEnabled = false;
  - BlendDescriptor alphaBlend;
  - BlendDescriptor colorBlend;
  + BlendDescriptor alphaBlend = {dawn::BlendOperation::Add, dawn::BlendFactor::One,
  + dawn::BlendFactor::Zero};
  + BlendDescriptor colorBlend = {dawn::BlendOperation::Add, dawn::BlendFactor::One,
  + dawn::BlendFactor::Zero};
  dawn::ColorWriteMask colorWriteMask = dawn::ColorWriteMask::All;
  };
  