Return error information from pdfium to JS.
This implements the previously unimplemented JS_Error() function.
Along the way:
- fix some IWYU when the include order in global.cpp was perturbed.
- remove some uses of JS_ErrorString, to increase transparency.
- use vp.IsSetting() in place of !vp.IsGetting() for clarity.
- specify an error string on several error return paths.
- add an error string for writing readonly properties.
- rename an error string constant to reflect the actual message.
- replace calls to variadic Format() with a function doing string appends.
- remove unused JS_GetClassName()
R=thestig@chromium.org
Review URL: https://codereview.chromium.org/963193003
14 files changed
