Google Maps fails with a GL assertion

[jdm]

./mach run http://maps.google.com

assertion failed: gl::check_frame_buffer_status(gl::FRAMEBUFFER) == gl::FRAMEBUFFER_COMPLETE (thread WebGLThread, at /Users/jdm/src/servo/./.cargo/registry/src/github.com-1ecc6299db9ec823/offscreen_gl_context-0.5.5/src/draw_buffer.rs:116)
stack backtrace:
   0:        0x106960671 - backtrace::backtrace::trace<closure>
                        at /Users/jdm/src/servo/./.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.0/src/backtrace/mod.rs:90
   1:        0x106961b64 - backtrace::capture::Backtrace::new::h8ca3ad60a3bf61a1
                        at /Users/jdm/src/servo/./.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.0/src/lib.rs:101
   2:        0x105aabb2b - servo::main::{{closure}}
                        at /Users/jdm/src/servo/ports/servo/main.rs:122
   3:        0x10bb6ba84 - std::panicking::rust_panic_with_hook::h8943f907023b7818
                        at /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libstd/panicking.rs:556
   4:        0x1068a1193 - std::panicking::begin_panic<&str>
                        at /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libstd/panicking.rs:517
   5:        0x106815c28 - offscreen_gl_context::draw_buffer::{{impl}}::new<offscreen_gl_context::platform::with_cgl::native_gl_context::NativeGLContext>
                        at /Users/jdm/src/servo/ports/servo/<panic macros>:3
   6:        0x1067af302 - offscreen_gl_context::gl_context::{{impl}}::create_draw_buffer<offscreen_gl_context::platform::with_cgl::native_gl_context::NativeGLContext>
                        at /Users/jdm/src/servo/./.cargo/registry/src/github.com-1ecc6299db9ec823/offscreen_gl_context-0.5.5/src/gl_context.rs:192
   7:        0x1067af117 - offscreen_gl_context::gl_context::{{impl}}::init_offscreen<offscreen_gl_context::platform::with_cgl::native_gl_context::NativeGLContext>
                        at /Users/jdm/src/servo/./.cargo/registry/src/github.com-1ecc6299db9ec823/offscreen_gl_context-0.5.5/src/gl_context.rs:179
   8:        0x1068dde8c - offscreen_gl_context::gl_context::{{impl}}::new_shared_with_dispatcher<offscreen_gl_context::platform::with_cgl::native_gl_context::NativeGLContext>
                        at /Users/jdm/src/servo/./.cargo/registry/src/github.com-1ecc6299db9ec823/offscreen_gl_context-0.5.5/src/gl_context.rs:85
   9:        0x1068ded26 - offscreen_gl_context::gl_context::{{impl}}::new<offscreen_gl_context::platform::with_cgl::native_gl_context::NativeGLContext>
                        at /Users/jdm/src/servo/./.cargo/registry/src/github.com-1ecc6299db9ec823/offscreen_gl_context-0.5.5/src/gl_context.rs:69
  10:        0x106906adf - canvas::webgl_paint_thread::{{impl}}::new
                        at /Users/jdm/src/servo/components/canvas/webgl_paint_thread.rs:33
  11:        0x10690730c - canvas::webgl_paint_thread::create_readback_painter
                        at /Users/jdm/src/servo/components/canvas/webgl_paint_thread.rs:102
  12:        0x106907dbc - canvas::webgl_paint_thread::{{impl}}::new
                        at /Users/jdm/src/servo/components/canvas/webgl_paint_thread.rs:130
  13:        0x106908b69 - canvas::webgl_paint_thread::{{impl}}::start::{{closure}}
                        at /Users/jdm/src/servo/components/canvas/webgl_paint_thread.rs:168
  14:        0x1068f9139 - std::panic::{{impl}}::call_once<(),closure>
                        at /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libstd/panic.rs:296
  15:        0x1068a1bad - std::panicking::try::do_call<std::panic::AssertUnwindSafe<closure>,()>
                        at /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libstd/panicking.rs:460
  16:        0x10bb6c99a - __rust_maybe_catch_panic
                        at /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libpanic_unwind/lib.rs:98
  17:        0x1068a163e - std::panicking::try<(),std::panic::AssertUnwindSafe<closure>>
                        at /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libstd/panicking.rs:436
  18:        0x10689f3bd - std::panic::catch_unwind<std::panic::AssertUnwindSafe<closure>,()>
                        at /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libstd/panic.rs:361
  19:        0x1068a0f29 - std::thread::{{impl}}::spawn::{{closure}}<closure,()>
                        at /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libstd/thread/mod.rs:357
  20:        0x1068c739e - alloc::boxed::{{impl}}::call_box<(),closure>
                        at /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/liballoc/boxed.rs:613
  21:        0x10bb6aa04 - std::sys::imp::thread::{{impl}}::new::thread_start
                        at /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/liballoc/boxed.rs:623
  22:     0x7fff91cdf898 - _pthread_body
  23:     0x7fff91cdf729 - _pthread_start

[jdm]

This is panicking at https://github.com/emilio/rust-offscreen-rendering-context/blob/b2c3fc73558d9ee8095439a49da3a7ccaad059df/src/draw_buffer.rs#L116.

[jdm]

I cannot reproduce this any more.