Option::unwrap() on None in script::dom::document::ElementFromPoint

[mateon1]

Found on http://sta.sh

called `Option::unwrap()` on a `None` value (thread ScriptThread PipelineId { namespace_id: PipelineNamespaceId(0), index: PipelineIndex(0) }, at /checkout/src/libcore/option.rs:335)
stack backtrace:
   0:     0x55d23f0292e4 - backtrace::backtrace::libunwind::trace
                        at /shared/dev/rust/servo/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.2/src/backtrace/libunwind.rs:53
                         - backtrace::backtrace::trace<closure>
                        at /shared/dev/rust/servo/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.2/src/backtrace/mod.rs:42
   1:     0x55d23f02386f - backtrace::capture::{{impl}}::new
                        at /shared/dev/rust/servo/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.2/src/capture.rs:64
   2:     0x55d23a756ccc - servo::main::{{closure}}
                        at /shared/dev/rust/servo/ports/servo/main.rs:130
   3:     0x55d241a3d316 - std::panicking::rust_panic_with_hook
                        at /checkout/src/libstd/panicking.rs:612
   4:     0x55d241a3d134 - std::panicking::begin_panic<alloc::string::String>
                        at /checkout/src/libstd/panicking.rs:572
   5:     0x55d241a3d0a9 - std::panicking::begin_panic_fmt
                        at /checkout/src/libstd/panicking.rs:522
   6:     0x55d241a3d03a - std::panicking::rust_begin_panic
                        at /checkout/src/libstd/panicking.rs:498
   7:     0x55d241a77660 - core::panicking::panic_fmt
                        at /checkout/src/libcore/panicking.rs:71
   8:     0x55d241a77596 - core::panicking::panic
                        at /checkout/src/libcore/panicking.rs:51
   9:     0x55d23c6299e6 - core::option::{{impl}}::unwrap<script_traits::WindowSizeData>
                        at /checkout/src/libcore/macros.rs:32
  10:     0x55d23cdd0a1e - script::dom::document::{{impl}}::ElementFromPoint
                        at /shared/dev/rust/servo/components/script/dom/document.rs:3627
  11:     0x55d23ea2202b - script::dom::bindings::codegen::Bindings::DocumentBinding::DocumentBinding::elementFromPoint::{{closure}}
                        at /shared/dev/rust/servo/target/debug/build/script-d00ee28330b6ecd4/out/Bindings/DocumentBinding.rs:3535
  12:     0x55d23e786e6f - core::ops::function::FnOnce::call_once<closure,()>
                        at /checkout/src/libcore/ops/function.rs:223
  13:     0x55d23e417aca - std::panic::{{impl}}::call_once<bool,closure>
                        at /checkout/src/libstd/panic.rs:296
  14:     0x55d23d30363c - std::panicking::try::do_call<std::panic::AssertUnwindSafe<closure>,bool>
                        at /checkout/src/libstd/panicking.rs:480
  15:     0x55d241a443bc - panic_unwind::__rust_maybe_catch_panic
                        at /checkout/src/libpanic_unwind/lib.rs:99
  16:     0x55d23d1b134d - std::panicking::try<bool,std::panic::AssertUnwindSafe<closure>>
                        at /checkout/src/libstd/panicking.rs:459
  17:     0x55d23e6af961 - std::panic::catch_unwind<std::panic::AssertUnwindSafe<closure>,bool>
                        at /checkout/src/libstd/panic.rs:361
  18:     0x55d23e4c2bd2 - js::panic::wrap_panic<std::panic::AssertUnwindSafe<closure>,bool>
                        at /shared/dev/rust/servo/.cargo/git/checkouts/rust-mozjs-8611526964119dd6/3de4ff3/src/panic.rs:22
  19:     0x55d23cf7e534 - script::dom::bindings::codegen::Bindings::DocumentBinding::DocumentBinding::elementFromPoint
                        at /shared/dev/rust/servo/target/debug/build/script-d00ee28330b6ecd4/out/Bindings/DocumentBinding.rs:3506
  20:     0x55d23f271fee - CallJitMethodOp
                        at /shared/dev/rust/servo/.cargo/git/checkouts/rust-mozjs-8611526964119dd6/3de4ff3/src/jsglue.cpp:516
  21:     0x55d23cd6d6be - script::dom::bindings::utils::generic_call
                        at /shared/dev/rust/servo/components/script/dom/bindings/utils.rs:446
  22:     0x55d23cd6d891 - script::dom::bindings::utils::generic_method
                        at /shared/dev/rust/servo/components/script/dom/bindings/utils.rs:454
  23:     0x55d23f8edf7b - _ZN2js12CallJSNativeEP9JSContextPFbS1_jPN2JS5ValueEERKNS2_8CallArgsE
                        at /shared/dev/rust/servo/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/834ce35/mozjs/js/src/jscntxtinlines.h:232
  24:     0x55d23f8bc3d3 - _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE
                        at /shared/dev/rust/servo/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/834ce35/mozjs/js/src/vm/Interpreter.cpp:453
  25:     0x55d23f8bc6fa - InternalCall
                        at /shared/dev/rust/servo/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/834ce35/mozjs/js/src/vm/Interpreter.cpp:498
  26:     0x55d23f8bc724 - _ZN2js13CallFromStackEP9JSContextRKN2JS8CallArgsE
                        at /shared/dev/rust/servo/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/834ce35/mozjs/js/src/vm/Interpreter.cpp:504
  27:     0x55d23f8c9750 - Interpret
                        at /shared/dev/rust/servo/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/834ce35/mozjs/js/src/vm/Interpreter.cpp:2873
  28:     0x55d23f8bc055 - _ZN2js9RunScriptEP9JSContextRNS_8RunStateE
                        at /shared/dev/rust/servo/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/834ce35/mozjs/js/src/vm/Interpreter.cpp:399
  29:     0x55d23f8bc4a2 - _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE
                        at /shared/dev/rust/servo/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/834ce35/mozjs/js/src/vm/Interpreter.cpp:471
  30:     0x55d23f8bc6fa - InternalCall
                        at /shared/dev/rust/servo/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/834ce35/mozjs/js/src/vm/Interpreter.cpp:498
  31:     0x55d23f8bc724 - _ZN2js13CallFromStackEP9JSContextRKN2JS8CallArgsE
                        at /shared/dev/rust/servo/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/834ce35/mozjs/js/src/vm/Interpreter.cpp:504
  32:     0x55d23f2ab880 - DoCallFallback
                        at /shared/dev/rust/servo/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/834ce35/mozjs/js/src/jit/BaselineIC.cpp:5970
  33:     0x7f563aba7e23 - <unknown>
ERROR:servo: called `Option::unwrap()` on a `None` value

[jdm]

Looks like the window is missing a window size at the point when we execute JS.

[mateon1]

Testcase (requires two files):

index.html

<iframe src="./aux.html" style="visibility: hidden"></iframe>

aux.html

<script>document.elementFromPoint(0,0);</script>