Add optional ANGLE support to glutin port
Supporting ANGLE in Servo has two important benefits:
* we can actually run Servo instances on our Windows CI machines, which gives us more confidence that we're not breaking it
* we can continue to use OpenGL on devices like the Hololens, rather than creating platform-specific graphical backends
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This removes paint threads, rust-layers dependency, and changes
optional webrender types to be required.
The use_webrender option has been removed, however I've left
the "-w" command line option in place so that wpt
runner can continue to pass that. Once it's removed from there
we can also remove the -w option.
Once this stage is complete, it should be fine to change the
display list building code to generate webrender display
lists directly and avoid the conversion step.
This implements system level DPI awareness for Windows. It has three
parts:
1. Add a application manifest which is copied alongside servo.exe during
build that declares our DPI awareness level. This is needed otherwise
DPI queries will return 96dpi and our application will be upscaled on
high DPI displays.
2. Rename hidpi_factor to avoid confusion with Glutin's hidpi_factor
which does something else.
3. Correctly convert windows sizes on window creation for
Windows. Unlike OS X, Windows uses device pixels for window creation.
* Sections like `[dependencies.foo]` can be entries in a `[dependencies]`
section with the `{key = value}` syntax.
* Per-target dependencies can be expressed with more general `cfg(…)`
conditions instead of exact target triples:
https://github.com/rust-lang/cargo/pull/2328
This changes headless operation to strictly be a runtime option, rather
than a compile-time one. Note that the old headless version still relied
on a display server to support WebGL, while it now requires one all the
time.
Fixes#8573
