This bug was filed from the Socorro interface and is report bp-fe0d74db-7b0f-45c6-abee-2d4160181205. > Mesa DRI Intel(R) Sandybridge Mobile > MOZ_CRASH Reason (Sanitized) > assertion failed: `(left != right)` > left: `0`, > right: `0`: glCopyImageSubData's behaviour is undefined if src and dst images are identical and the rectangles overlap. This assertion has been added by bug 1510379. ============================================================= Top 10 frames of crashing thread: 0 libxul.so MOZ_CrashOOL mfbt/Assertions.h:314 1 libxul.so GeckoCrashOOL toolkit/xre/nsAppRunner.cpp:5124 2 libxul.so gkrust_shared::panic_hook toolkit/library/rust/shared/lib.rs:234 3 libxul.so core::ops::function::Fn::call libcore/ops/function.rs:78 4 libxul.so std::panicking::rust_panic_with_hook /rustc/da5f414c2c0bfe5198934493f04c676e2b23ff2e/src/libstd/panicking.rs:481 5 libxul.so std::panicking::continue_panic_fmt /rustc/da5f414c2c0bfe5198934493f04c676e2b23ff2e/src/libstd/panicking.rs:391 6 libxul.so std::panicking::begin_panic_fmt /rustc/da5f414c2c0bfe5198934493f04c676e2b23ff2e/src/libstd/panicking.rs:346 7 libxul.so webrender::device::gl::Device::blit_renderable_texture gfx/wr/webrender/src/device/gl.rs:1762 8 libxul.so webrender::renderer::Renderer::update_texture_cache gfx/wr/webrender/src/renderer.rs:2846 9 libxul.so webrender::renderer::Renderer::render_impl gfx/wr/webrender/src/renderer.rs:2552 =============================================================

Hmm, the assertion was put in to avoid copying with the same texture as src and dst. But the fact that src.id and dst.id are zero is particularly odd. I don't think that should be possible, so something has gone wrong.