Merge m-c to inbound, a=merge

browser/app/profile/firefox.js

browser/base/content/aboutNetError.xhtml

browser/base/content/browser.css

browser/base/content/illustrations/error-malformed-url.svg

browser/base/content/test/general/browser_discovery.js

...nt/test/general/browser_favicon_change_not_in_document.js

...ontent/test/general/browser_subframe_favicons_not_used.js

...t/test/performance/browser_urlbar_keyed_search_reflows.js

...content/test/performance/browser_urlbar_search_reflows.js

browser/base/content/test/performance/head.js

browser/base/content/test/popupNotifications/browser.ini

...fications/browser_popupNotification_selection_required.js

...tent/test/webrtc/browser_devices_get_user_media_screen.js

...ebrtc/browser_devices_get_user_media_unprompted_access.js

browser/base/jar.mn

browser/components/customizableui/CustomizableUI.jsm

browser/components/customizableui/content/panelUI.inc.xul

browser/components/customizableui/content/panelUI.js

browser/components/customizableui/test/browser.ini

...s/customizableui/test/browser_insert_before_moved_node.js