Make command buffer commands and immediate data volatile

gpu/command_buffer/common/cmd_buffer_common.h

Index: gpu/command_buffer/common/cmd_buffer_common.h
diff --git a/gpu/command_buffer/common/cmd_buffer_common.h b/gpu/command_buffer/common/cmd_buffer_common.h
index e8989be2894cd07a60fa4a04dce85e53d5d398c0..38acf4a6e9cde51386ed95daa102638c080c65b0 100644
--- a/gpu/command_buffer/common/cmd_buffer_common.h
+++ b/gpu/command_buffer/common/cmd_buffer_common.h
@@ -79,6 +79,11 @@ struct CommandHeader {
     DCHECK_GE(size_in_bytes, sizeof(T));  // NOLINT
     Init(T::kCmdId, ComputeNumEntries(size_in_bytes));
   }
+
+  static CommandHeader FromVolatile(const volatile CommandHeader& other) {
+    // const_cast is safe because the copy constructor is trivial.
+    return const_cast<const CommandHeader&>(other);
+  }
 };
 
 static_assert(sizeof(CommandHeader) == 4,