Refactor context creation parameters into a struct.

gpu/gles2_conform_support/egl/context.cc

Index: gpu/gles2_conform_support/egl/context.cc
diff --git a/gpu/gles2_conform_support/egl/context.cc b/gpu/gles2_conform_support/egl/context.cc
index 001e4979d87d3b206098a190d0184d2fefeaae8a..2d870e7dc2dca6c0317e68995195ee306d4083e0 100644
--- a/gpu/gles2_conform_support/egl/context.cc
+++ b/gpu/gles2_conform_support/egl/context.cc
@@ -273,8 +273,10 @@ bool Context::CreateService(gl::GLSurface* gl_surface) {
 
   decoder->set_engine(command_executor.get());
 
+  gl::GLContextAttribs context_attribs;
+  context_attribs.gpu_preference = gl::PreferDiscreteGpu;
   scoped_refptr<gl::GLContext> gl_context(
-      gl::init::CreateGLContext(nullptr, gl_surface, gl::PreferDiscreteGpu));
+      gl::init::CreateGLContext(nullptr, gl_surface, context_attribs));
   if (!gl_context)
     return false;