gpu: Use explicit atomics instead of assuming that 32bit read/writes are atomic.

gpu/command_buffer/common/gles2_cmd_format.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 defines the GLES2 command buffer commands.
 
 #ifndef GPU_COMMAND_BUFFER_COMMON_GLES2_CMD_FORMAT_H_
 #define GPU_COMMAND_BUFFER_COMMON_GLES2_CMD_FORMAT_H_
 
 
 #include <KHR/khrplatform.h>
 
 #include <string.h>
 
+#include "base/atomicops.h"
 #include "gpu/command_buffer/common/bitfield_helpers.h"
 #include "gpu/command_buffer/common/cmd_buffer_common.h"
 #include "gpu/command_buffer/common/gles2_cmd_ids.h"
 #include "gpu/command_buffer/common/types.h"
 
 // GL types are forward declared to avoid including the GL headers. The problem
 // is determining which GL headers to include from code that is common to the
 // client and service sides (GLES2 or one of several GL implementations).
 typedef unsigned int GLenum;
 typedef unsigned int GLbitfield;
@@ skipping 115 matching lines @@
   // ProgramInput inputs[num_attribs + num_uniforms];
 };
 
 // The format of QuerySync used by EXT_occlusion_query_boolean
 struct QuerySync {
   void Reset() {
     process_count = 0;
     result = 0;
   }
 
-  uint32 process_count;
+  base::subtle::Atomic32 process_count;
   uint64 result;
 };
 
 COMPILE_ASSERT(sizeof(ProgramInput) == 20, ProgramInput_size_not_20);
 COMPILE_ASSERT(offsetof(ProgramInput, type) == 0,
                OffsetOf_ProgramInput_type_not_0);
 COMPILE_ASSERT(offsetof(ProgramInput, size) == 4,
                OffsetOf_ProgramInput_size_not_4);
 COMPILE_ASSERT(offsetof(ProgramInput, location_offset) == 8,
                OffsetOf_ProgramInput_location_offset_not_8);
@@ skipping 278 matching lines @@
   CommandHeader header;
 };
 
 #pragma pack(pop)
 
 }  // namespace cmd
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_COMMON_GLES2_CMD_FORMAT_H_