Mojo: Implement MojoUnmapBuffer().

mojo/system/core_impl.h

Index: mojo/system/core_impl.h
diff --git a/mojo/system/core_impl.h b/mojo/system/core_impl.h
index 63b4b08b949cb3db330eb8d172b8b61ff640873a..e0cbd1e3951cd2cc06aaf27c9d117a0829f2aa1a 100644
--- a/mojo/system/core_impl.h
+++ b/mojo/system/core_impl.h
@@ -11,6 +11,7 @@
 #include "base/synchronization/lock.h"
 #include "mojo/public/system/core_private.h"
 #include "mojo/system/handle_table.h"
+#include "mojo/system/mapping_table.h"
 #include "mojo/system/system_impl_export.h"
 
 namespace mojo {
@@ -138,6 +139,9 @@ class MOJO_SYSTEM_IMPL_EXPORT CoreImpl : public Core {
   base::Lock handle_table_lock_;  // Protects |handle_table_|.
   HandleTable handle_table_;
 
+  base::Lock mapping_table_lock_;  // Protects |mapping_table_|.
+  MappingTable mapping_table_;
+
   // ---------------------------------------------------------------------------
 
   DISALLOW_COPY_AND_ASSIGN(CoreImpl);