Since m117:
- Remove GrBackendSurfaceMutableState
- Remove bridge code for legacy GL GrBackendSurface code
- GrBackendFormat::MakeGL, GrBackendFormat::asGLFormat, GrBackendTexture::getGLTextureInfo, GrBackendTexture::glTextureParametersModified, GrBackendRenderTarget::getGLFramebufferInfo, now emulated
- GL-related GrBackendTexture, GrBackendRenderTarget constructors removed (m119 adds emulation for these)