webgl: Unlock WebRender by default by adding a readback based fallback to WebGL context creation.
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This should give us the chance to use WebRender by default in OSX.
r? @pcwalton
cc @glennw @larsbergstrom
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This allows keeping the VertexAttrib* calls asynchronous.
Another option would be to do the validation in the apply() function,
but that'd require us passing an unnecessary channel around and add
extra synchronization.
The counterpart of this is that it has to be updated when the context
changes, but that's less problem.
WebRender is an experimental GPU accelerated rendering backend for Servo.
The WebRender backend can be specified by running Servo with the -w option (otherwise the default rendering backend will be used).
WebRender has many bugs, and missing features - but it is usable to browse most websites - please report any WebRender specific rendering bugs you encounter!
Hopefully the build machines and everyone using Servo has GL 3.3 available on their machines - if it causes any problems, we can revert this change and investigate further.
I was going to implement Uniform4fv with sequences, (since it
practically implemented), but we can't until we support Float32Array
args because codegen doesn't know how tu differenciate between both.
