Remove usage of FOR_EACH_OBSERVER macro in gpu

gpu/ipc/client/command_buffer_proxy_impl.cc

Index: gpu/ipc/client/command_buffer_proxy_impl.cc
diff --git a/gpu/ipc/client/command_buffer_proxy_impl.cc b/gpu/ipc/client/command_buffer_proxy_impl.cc
index 0ce0b8d8a56a6894f15d4ee9a96330cba2e734f0..2ea77b34fdb4b7839481cb452077732abb2cfa5f 100644
--- a/gpu/ipc/client/command_buffer_proxy_impl.cc
+++ b/gpu/ipc/client/command_buffer_proxy_impl.cc
@@ -100,7 +100,8 @@ std::unique_ptr<CommandBufferProxyImpl> CommandBufferProxyImpl::Create(
 }
 
 CommandBufferProxyImpl::~CommandBufferProxyImpl() {
-  FOR_EACH_OBSERVER(DeletionObserver, deletion_observers_, OnWillDeleteImpl());
+  for (auto& observer : deletion_observers_)
+    observer.OnWillDeleteImpl();
   DisconnectChannel();
 }