gpu: Cleanup class/struct forward declarations

gpu/ipc/service/gpu_channel_manager_delegate.h

Index: gpu/ipc/service/gpu_channel_manager_delegate.h
diff --git a/gpu/ipc/service/gpu_channel_manager_delegate.h b/gpu/ipc/service/gpu_channel_manager_delegate.h
index 419cc8c1ac1664fb201facfa1428beabdf0177ac..9201a5391a10348ff91943b38114fca0c5466f81 100644
--- a/gpu/ipc/service/gpu_channel_manager_delegate.h
+++ b/gpu/ipc/service/gpu_channel_manager_delegate.h
@@ -10,14 +10,8 @@
 
 class GURL;
 
-namespace IPC {
-struct ChannelHandle;
-}
-
 namespace gpu {
 
-struct GPUMemoryUmaStats;
-
 class GpuChannelManagerDelegate {
  public:
   // Tells the delegate that an offscreen context was created for the provided