ozone: Introduce ClientPixmap and ClientPixmapFactory for non-GPU processes.

ui/ozone/public/ozone_platform.cc

Index: ui/ozone/public/ozone_platform.cc
diff --git a/ui/ozone/public/ozone_platform.cc b/ui/ozone/public/ozone_platform.cc
index b69bc28927d76d800321b2f58b2c26c66759d21d..a3eace7c4ea3531dea00b2d58d28737c6f37c606 100644
--- a/ui/ozone/public/ozone_platform.cc
+++ b/ui/ozone/public/ozone_platform.cc
@@ -8,6 +8,7 @@
 #include "ui/events/devices/device_data_manager.h"
 #include "ui/ozone/platform_object.h"
 #include "ui/ozone/platform_selection.h"
+#include "ui/ozone/public/ozone_client.h"
 #include "ui/ozone/public/ozone_platform.h"
 #include "ui/ozone/public/ozone_switches.h"
 
@@ -42,6 +43,8 @@ void OzonePlatform::InitializeForUI() {
   // This is deliberately created after initializing so that the platform can
   // create its own version of DDM.
   DeviceDataManager::CreateInstance();
+
+  OzoneClient::InitializeForUI();
 }
 
 // static