Remove deprecated Ozone initialization functions.

ui/ozone/platform/drm/ozone_platform_gbm.cc

Index: ui/ozone/platform/drm/ozone_platform_gbm.cc
diff --git a/ui/ozone/platform/drm/ozone_platform_gbm.cc b/ui/ozone/platform/drm/ozone_platform_gbm.cc
index 0e2fdc1398c416807bbf487c52d2b1b73a103392..89b42aa5400c7cb92a59e270b436874d00eb86c0 100644
--- a/ui/ozone/platform/drm/ozone_platform_gbm.cc
+++ b/ui/ozone/platform/drm/ozone_platform_gbm.cc
@@ -139,10 +139,6 @@ class OzonePlatformGbm
       override {
     return base::MakeUnique<DrmNativeDisplayDelegate>(display_manager_.get());
   }
-  void InitializeUI() override {
-    InitParams default_params;
-    InitializeUI(default_params);
-  }
   void InitializeUI(const InitParams& args) override {
     // Ozone drm can operate in three modes configured at runtime:
     //   1. legacy mode where browser and gpu components communicate
@@ -207,10 +203,6 @@ class OzonePlatformGbm
                                          overlay_manager_.get());
     }
   }
-  void InitializeGPU() override {
-    InitParams default_params;
-    InitializeGPU(default_params);
-  }
   void InitializeGPU(const InitParams& args) override {
     // TODO(rjkroege): services/ui should initialize this with a connector.
     // However, in-progress refactorings in services/ui make it difficult to