Refactor #[jstraceable] to #[derive(JSTraceable)]
fixes#6524. I had to make an additional change not mentioned in the ticket - adding the `#[feature]` to enable deriving custom traits but I assume that's expected at this time.
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Update to latest rust-layers
The compositing context, painting context and display metadata have all
been collapsed into a single NativeDisplay class.
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Add keyboard shortcuts to glutin browser
Supersedes #6488. Changes since then:
* Fix a few places where we needed cfg(feature = "window") in order to compile without the feature.
* Zoom-in shortcut now works both with and without shift. (Uses a guard because I couldn't think of another way to do it without CTFE.)
* Back/forward shortcuts now correctly use Alt on non-Mac platforms.
* The back/forward shortcuts that use square brackets are now non-Windows, rather than Mac-only. This roughly matches XP_UNIX: http://hg.mozilla.org/mozilla-central/file/d4c4ce7f060c/browser/base/content/browser-sets.inc#l354
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This commit was generated using the following commands:
```
find . -iname "*.webidl" -type f -print0 | xargs -0 sed -i '' 's/http:\(.*\)github.io/https:\1github.io/g'
```
```
find . -iname "*.rs" -type f -print0 | xargs -0 sed -i '' 's/http:\(.*\)github.io/https:\1github.io/g'
```
Use an atomic bool for EXPERIMENTAL_ENABLED.
static mut smells, especially as it can be set and read from multiple threads
(for example in unit tests).
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Use a dedicated type for the opaque type parameter to WorkQueue in layout.
Currently, we use UnsafeFlow and UnsafeLayoutNode, both of which are aliases
for (usize, usize) and thus interconvertible. This change should make it
clearer that the WorkQueue is not limited to one particular type.
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Update to zero-copy* HTML parsing
html5ever now uses the Tendril string type to minimize copying internally, but Servo still converts from/to `String` at the boundary (which involves copying).
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