The devtools theme is no longer relevant when dealing with compact themes, since it doesn't
affect the theme colors. But we still need it for styling other things related to devtools
in browser.xul, like the splitter between the toolbox and page and gcli.
MozReview-Commit-ID: 2CXDuwQY19x
This commit does the following:
* Install two lightweight themes instead of one
* Introduce a build config to install the themes instead of relying on channel: INSTALL_COMPACT_THEMES
* Change browser-compacttheme to use the new themes instead of the old one
* Remove inferBrightness since the lwt colors are part of the compact theme definision, as opposed
to the devedition theme which could be light or
* Update CSS to use :-moz-lwtheme-darktext and :-moz-lwtheme-brighttext instead of [devtoolstheme]
MozReview-Commit-ID: 4gKU68drlE2
