Revert of [Ozone-GBM] Handle GPU crashes

ui/ozone/platform/dri/gpu_platform_support_host_gbm.h

Index: ui/ozone/platform/dri/gpu_platform_support_host_gbm.h
diff --git a/ui/ozone/platform/dri/gpu_platform_support_host_gbm.h b/ui/ozone/platform/dri/gpu_platform_support_host_gbm.h
index 2e6c36000edc6b02fad8705956d6825d0775dd02..4887bae5b4e485fea0eb059301b528c1c1fce998 100644
--- a/ui/ozone/platform/dri/gpu_platform_support_host_gbm.h
+++ b/ui/ozone/platform/dri/gpu_platform_support_host_gbm.h
@@ -8,7 +8,6 @@
 #include <queue>
 #include <vector>
 
-#include "base/observer_list.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/ozone/platform/dri/hardware_cursor_delegate.h"
 #include "ui/ozone/public/gpu_platform_support_host.h"
@@ -21,8 +20,6 @@
 
 namespace ui {
 
-class ChannelObserver;
-
 class GpuPlatformSupportHostGbm : public GpuPlatformSupportHost,
                                   public HardwareCursorDelegate,
                                   public IPC::Sender {
@@ -32,9 +29,6 @@
 
   void RegisterHandler(GpuPlatformSupportHost* handler);
   void UnregisterHandler(GpuPlatformSupportHost* handler);
-
-  void AddChannelObserver(ChannelObserver* observer);
-  void RemoveChannelObserver(ChannelObserver* observer);
 
   // GpuPlatformSupportHost:
   virtual void OnChannelEstablished(int host_id, IPC::Sender* sender) OVERRIDE;
@@ -61,7 +55,6 @@
   // delay sending them until the channel is created. These messages are stored
   // in |queued_messaged_|.
   std::queue<IPC::Message*> queued_messages_;
-  ObserverList<ChannelObserver> channel_observers_;
 };
 
 }  // namespace ui