Bug 959677.  Fail codegen if a writable attribute is flagged PutForwards or Replaceable.  r=smaug
Bug 959679.  Use a handle, not a raw value, to avoid a rooting issue in canvas code.  r=terrence
Bug 959695 part 1.  Make ValueToCallable take a Handle.  r=terrence
Bug 959695 part 2.  Make ReportIfNotFunction take a Handle.  r=terrence
Bug 959695 part 3.  Make ReportIsNotFunction take a Handle.  r=terrence
Bug 959705.  Fix unsafe reference hazards in xpconnect code.  r=bholley
Bug 851891.  Make stringifier attributes fail to codegen.  r=khuey