Introducing gpu::CommandBufferId as a distinct, IdType<...>-based type.

ppapi/proxy/ppapi_command_buffer_proxy.h

Index: ppapi/proxy/ppapi_command_buffer_proxy.h
diff --git a/ppapi/proxy/ppapi_command_buffer_proxy.h b/ppapi/proxy/ppapi_command_buffer_proxy.h
index 486e310ddf824c3dc5411fd03382dc8b1e910d33..e0629bf4bb31076a3d93a53a5636f8c5b1d7612b 100644
--- a/ppapi/proxy/ppapi_command_buffer_proxy.h
+++ b/ppapi/proxy/ppapi_command_buffer_proxy.h
@@ -14,6 +14,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "gpu/command_buffer/client/gpu_control.h"
 #include "gpu/command_buffer/common/command_buffer.h"
+#include "gpu/command_buffer/common/command_buffer_id.h"
 #include "gpu/command_buffer/common/command_buffer_shared.h"
 #include "ppapi/proxy/plugin_dispatcher.h"
 #include "ppapi/proxy/ppapi_proxy_export.h"
@@ -35,7 +36,7 @@ class PPAPI_PROXY_EXPORT PpapiCommandBufferProxy : public gpu::CommandBuffer,
                           PluginDispatcher* dispatcher,
                           const gpu::Capabilities& capabilities,
                           const SerializedHandle& shared_state,
-                          uint64_t command_buffer_id);
+                          gpu::CommandBufferId command_buffer_id);
   ~PpapiCommandBufferProxy() override;
 
   // gpu::CommandBuffer implementation:
@@ -67,7 +68,7 @@ class PPAPI_PROXY_EXPORT PpapiCommandBufferProxy : public gpu::CommandBuffer,
   bool IsGpuChannelLost() override;
   void EnsureWorkVisible() override;
   gpu::CommandBufferNamespace GetNamespaceID() const override;
-  uint64_t GetCommandBufferID() const override;
+  gpu::CommandBufferId GetCommandBufferID() const override;
   uint64_t GenerateFenceSyncRelease() override;
   bool IsFenceSyncRelease(uint64_t release) override;
   bool IsFenceSyncFlushed(uint64_t release) override;
@@ -89,7 +90,7 @@ class PPAPI_PROXY_EXPORT PpapiCommandBufferProxy : public gpu::CommandBuffer,
 
   void FlushInternal();
 
-  const uint64_t command_buffer_id_;
+  const gpu::CommandBufferId command_buffer_id_;
 
   gpu::Capabilities capabilities_;
   State last_state_;