gpu: Add GpuFence framework.

ppapi/proxy/ppapi_command_buffer_proxy.cc

Index: ppapi/proxy/ppapi_command_buffer_proxy.cc
diff --git a/ppapi/proxy/ppapi_command_buffer_proxy.cc b/ppapi/proxy/ppapi_command_buffer_proxy.cc
index 77ef28217f98a9e8316a1eac4ed92494a61e62b6..22e8224f0cbd8c7b3b2fce00788d424581a18e2c 100644
--- a/ppapi/proxy/ppapi_command_buffer_proxy.cc
+++ b/ppapi/proxy/ppapi_command_buffer_proxy.cc
@@ -223,6 +223,15 @@ bool PpapiCommandBufferProxy::CanWaitUnverifiedSyncToken(
   return false;
 }
 
+int32_t PpapiCommandBufferProxy::CreateFence(ClientFence fence) {
+  NOTIMPLEMENTED();
+  return -1;
+}
+
+void PpapiCommandBufferProxy::DestroyFence(int32_t id) {
+  NOTIMPLEMENTED();
+}
+
 int32_t PpapiCommandBufferProxy::GetExtraCommandBufferData() const {
   return 0;
 }