In the old inspector, this file was generated as a build step from Inspector.json. It would be nice to carry this over to the new inspector build process, since it seems folks have been copying the autogenerated output from the old one anyway.
<rdar://problem/14219290>
The process would be to have WebInspectorUI project copy the generated version from WebCore.framework.
*** This bug has been marked as a duplicate of bug 120242 ***