Make command buffer commands and immediate data volatile

gpu/command_buffer/common/cmd_buffer_common.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains the common parts of command buffer formats.
 
 #ifndef GPU_COMMAND_BUFFER_COMMON_CMD_BUFFER_COMMON_H_
 #define GPU_COMMAND_BUFFER_COMMON_CMD_BUFFER_COMMON_H_
 
 #include <stddef.h>
@@ skipping 61 matching lines @@
   }
 
   // Sets the header by a size in bytes.
   template <typename T>
   void SetCmdByTotalSize(uint32_t size_in_bytes) {
     static_assert(T::kArgFlags == cmd::kAtLeastN,
                   "T::kArgFlags should equal cmd::kAtLeastN");
     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,
               "size of CommandHeader should equal 4");
 
 // Union that defines possible command buffer entries.
 union CommandBufferEntry {
   CommandHeader value_header;
   uint32_t value_uint32;
   int32_t value_int32;
@@ skipping 458 matching lines @@
               "offset of GetBucketData.shared_memory_offset should be 20");
 
 }  // namespace cmd
 
 #pragma pack(pop)
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_COMMON_CMD_BUFFER_COMMON_H_