[Ozone-Drm] Revert of holding on to the DRM FDs in the browser process

ui/ozone/platform/drm/host/drm_display_host_manager.h

Index: ui/ozone/platform/drm/host/drm_display_host_manager.h
diff --git a/ui/ozone/platform/drm/host/drm_display_host_manager.h b/ui/ozone/platform/drm/host/drm_display_host_manager.h
index fbebd177f7fd310307b58e92e814c36e35803bfc..f5ae2b831e31e363215787c1e18056afde726ef9 100644
--- a/ui/ozone/platform/drm/host/drm_display_host_manager.h
+++ b/ui/ozone/platform/drm/host/drm_display_host_manager.h
@@ -7,8 +7,8 @@
 
 #include <map>
 #include <queue>
+#include <set>
 
-#include "base/containers/scoped_ptr_hash_map.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
@@ -132,8 +132,11 @@ class DrmDisplayHostManager : public DeviceEventObserver,
   bool task_pending_;
 
   // Keeps track of all the active DRM devices.
-  base::ScopedPtrHashMap<base::FilePath, scoped_ptr<DrmDeviceHandle>>
-      drm_devices_;
+  std::set<base::FilePath> drm_devices_;
+
+  // This is used to cache the primary DRM device until the channel is
+  // established.
+  scoped_ptr<DrmDeviceHandle> primary_drm_device_handle_;
 
   base::WeakPtrFactory<DrmDisplayHostManager> weak_ptr_factory_;