Added a unique command buffer ID for command buffers.

gpu/command_buffer/common/constants.h

Index: gpu/command_buffer/common/constants.h
diff --git a/gpu/command_buffer/common/constants.h b/gpu/command_buffer/common/constants.h
index d06836c0d71ea9e5a5c871db8ef79f75ea424eca..0b312eded1eec448a9104018849fc7c6ae435f50 100644
--- a/gpu/command_buffer/common/constants.h
+++ b/gpu/command_buffer/common/constants.h
@@ -66,6 +66,18 @@ const int32_t kCommandBufferSharedMemoryId = 4;
 // The size to set for the program cache.
 const size_t kDefaultMaxProgramCacheMemoryBytes = 6 * 1024 * 1024;
 
+// Namespace used to separate various command buffer types.
+enum CommandBufferNamespace {
+  kCommandBufferNamespace_Invalid = -1,
+
+  kCommandBufferNamespace_GpuIO,
+  kCommandBufferNamespace_InProcess,
+  kCommandBufferNamespace_Mojo,
+
+  NUM_COMMAND_BUFFER_NAMESPACES
+};
+
+
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_COMMON_CONSTANTS_H_