ozone: Make CreateScreen pure virtual.

We have all the Ozone platforms implementing the PlatformScreen.

Now, it's the time to make that method pure virtual.

However, there is one point - Ozone/Drm and Cast do not support
PlatformScreen, but still implement it and expect that the
method is not reached.

Bug: 872339
Change-Id: I628878842294a8e99033893a9be42026066c29c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869004Reviewed-by: Michael Spang <spang@chromium.org>
Commit-Queue: Maksim Sisov <msisov@igalia.com>
Cr-Commit-Position: refs/heads/master@{#712927}

ui/ozone/platform/cast/ozone_platform_cast.cc

@@ -27,6 +27,7 @@
 #include "ui/ozone/public/gpu_platform_support_host.h"
 #include "ui/ozone/public/input_controller.h"
 #include "ui/ozone/public/ozone_platform.h"
+#include "ui/ozone/public/platform_screen.h"
 #include "ui/ozone/public/system_input_injector.h"
 #include "ui/platform_window/platform_window_init_properties.h"
 
@@ -87,6 +88,10 @@ class OzonePlatformCast : public OzonePlatform {
   InputController* GetInputController() override {
     return event_factory_ozone_->input_controller();
   }
+  std::unique_ptr<PlatformScreen> CreateScreen() override {
+    NOTREACHED();
+    return nullptr;
+  }
   GpuPlatformSupportHost* GetGpuPlatformSupportHost() override {
     return gpu_platform_support_host_.get();
   }

ui/ozone/platform/drm/ozone_platform_gbm.cc

@@ -12,6 +12,7 @@
 
 #include "base/bind.h"
 #include "base/command_line.h"
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/platform_thread.h"
@@ -49,6 +50,7 @@
 #include "ui/ozone/public/mojom/drm_device.mojom.h"
 #include "ui/ozone/public/ozone_platform.h"
 #include "ui/ozone/public/ozone_switches.h"
+#include "ui/ozone/public/platform_screen.h"
 #include "ui/platform_window/platform_window_init_properties.h"
 
 #if BUILDFLAG(USE_XKBCOMMON)
@@ -94,6 +96,11 @@ class OzonePlatformGbm : public OzonePlatform {
     }
   }
 
+  std::unique_ptr<PlatformScreen> CreateScreen() override {
+    NOTREACHED();
+    return nullptr;
+  }
+
   GpuPlatformSupportHost* GetGpuPlatformSupportHost() override {
     if (using_mojo_) {
       return drm_device_connector_.get();

ui/ozone/public/ozone_platform.cc

@@ -82,10 +82,6 @@ IPC::MessageFilter* OzonePlatform::GetGpuMessageFilter() {
   return nullptr;
 }
 
-std::unique_ptr<PlatformScreen> OzonePlatform::CreateScreen() {
-  return nullptr;
-}
-
 PlatformClipboard* OzonePlatform::GetPlatformClipboard() {
   // Platforms that support system clipboard must override this method.
   return nullptr;

ui/ozone/public/ozone_platform.h

@@ -155,7 +155,7 @@ class COMPONENT_EXPORT(OZONE) OzonePlatform {
       PlatformWindowInitProperties properties) = 0;
   virtual std::unique_ptr<display::NativeDisplayDelegate>
   CreateNativeDisplayDelegate() = 0;
-  virtual std::unique_ptr<PlatformScreen> CreateScreen();
+  virtual std::unique_ptr<PlatformScreen> CreateScreen() = 0;
   virtual PlatformClipboard* GetPlatformClipboard();
   virtual std::unique_ptr<InputMethod> CreateInputMethod(
       internal::InputMethodDelegate* delegate) = 0;