Consolidate OutputSurface constructors into GL vs Vulkan.

cc/surfaces/surface_display_output_surface.cc

Index: cc/surfaces/surface_display_output_surface.cc
diff --git a/cc/surfaces/surface_display_output_surface.cc b/cc/surfaces/surface_display_output_surface.cc
index 749791ef0de34c2a59c73409dbb9915b63cc437c..6fb7d79bdf4b4bfacf099ec87703eaeb2a3536cd 100644
--- a/cc/surfaces/surface_display_output_surface.cc
+++ b/cc/surfaces/surface_display_output_surface.cc
@@ -20,7 +20,8 @@ SurfaceDisplayOutputSurface::SurfaceDisplayOutputSurface(
     scoped_refptr<ContextProvider> context_provider,
     scoped_refptr<ContextProvider> worker_context_provider)
     : OutputSurface(std::move(context_provider),
-                    std::move(worker_context_provider)),
+                    std::move(worker_context_provider),
+                    nullptr),
       display_client_(nullptr),
       factory_(surface_manager, this),
       allocator_(allocator) {
@@ -37,10 +38,7 @@ SurfaceDisplayOutputSurface::SurfaceDisplayOutputSurface(
     SurfaceManager* surface_manager,
     SurfaceIdAllocator* allocator,
     scoped_refptr<VulkanContextProvider> vulkan_context_provider)
-    : OutputSurface(nullptr,
-                    nullptr,
-                    std::move(vulkan_context_provider),
-                    nullptr),
+    : OutputSurface(std::move(vulkan_context_provider), nullptr),
       display_client_(NULL),
       factory_(surface_manager, this),
       allocator_(allocator) {