Refactor context creation parameters into a struct.

ui/gl/gl_context_cgl.cc

Index: ui/gl/gl_context_cgl.cc
diff --git a/ui/gl/gl_context_cgl.cc b/ui/gl/gl_context_cgl.cc
index 8ad268996ab7fdd872df55cc891e9a036d34b673..5107e73c9acf005b51db118349a74508978808ef 100644
--- a/ui/gl/gl_context_cgl.cc
+++ b/ui/gl/gl_context_cgl.cc
@@ -91,11 +91,12 @@ GLContextCGL::GLContextCGL(GLShareGroup* share_group)
 }
 
 bool GLContextCGL::Initialize(GLSurface* compatible_surface,
-                              GpuPreference gpu_preference) {
+                              const GLContextAttribs& attribs) {

[piman, 2016/11/07 21:01:01]

Here and other context types: I think we should fail Initialize() if we request
features that are not available (!bind_generates_resources,
webgl_compatibility_context). Otherwise it could lead to confusion and bugs.

[Geoff Lang, 2016/11/07 21:36:21]

Done, I used a DCHECK but can change it to a failure if needed.

   DCHECK(compatible_surface);
 
-  gpu_preference = ui::GpuSwitchingManager::GetInstance()->AdjustGpuPreference(
-      gpu_preference);
+  GpuPreference gpu_preference =
+      ui::GpuSwitchingManager::GetInstance()->AdjustGpuPreference(
+          attribs.gpu_preference);
 
   GLContextCGL* share_context = share_group() ?
       static_cast<GLContextCGL*>(share_group()->GetContext()) : nullptr;