Supports creating a windowless browser on Linux without an X server. Most of the
changes are just adding branches to avoid calls in to GTK which calls
into X. Some of the bigger additions were adding a separate headless widget
which implements just enough to render a page. A headless look and
feel were also added since there are many calls into GTK in the platform
specific one.
ScreenHelperGTK is the platform dependent part of the original
nsScreenManagerGtk and nsScreenGtk. It registers monitors-changed
event listener from gtk and pushes updates to ScreenManager. See patch
part 4. for how ScreenManager works.
MozReview-Commit-ID: KBo7ZLFTjM3
Changes to nsIScreen and nsIScreenManager were reviewed by roc.
Changes to dom/ipc were reviewed by jimm.
Changes to gfx/src/nsDeviceContext.cpp were reviewed by roc.
Changes to widget/android were reviewed by snorp.
Changes to widget/cocoa were reviewed by smichaud.
Changes to widget/gtk were reviewed by roc.
Changes to widget/windows were reviewed by jimm.
Changes to widget/xpwidgets were reviewed by roc.
Changes to nsIScreen and nsIScreenManager were reviewed by roc.
Changes to dom/ipc were reviewed by jimm.
Changes to gfx/src/nsDeviceContext.cpp were reviewed by roc.
Changes to widget/android were reviewed by snorp.
Changes to widget/cocoa were reviewed by smichaud.
Changes to widget/gtk were reviewed by roc.
Changes to widget/windows were reviewed by jimm.
Changes to widget/xpwidgets were reviewed by roc.
