User scripts that throw an exception during initial execution trigger a panic

[jdm]

This happens because the error event is fired, and the script is executed while the parser is active (and thus any document.write call would trigger a borrow error). We should probably find a way to treat this more like an inline script element, rather than executing the JS directly.

[2019-01-15T19:34:59Z ERROR script::dom::bindings::error] Error at :1:0 illegal character
assertion failed: window.Document().can_invoke_script() (thread ScriptThread PipelineId { namespace_id: PipelineNamespaceId(1), index: PipelineIndex(2) }, at components/script/dom/eventtarget.rs:378)
stack backtrace:
   0:        0x113ae5e64 - __ZN9backtrace9backtrace5trace17h639040ad2b3cb7adE
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.9/src/backtrace/mod.rs:42
   1:        0x113adf03c - __ZN9backtrace7capture9Backtrace14new_unresolved17hfc3d3fdb95744dbfE
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.9/src/capture.rs:88
   2:        0x113adef9e - __ZN9backtrace7capture9Backtrace3new17h1adc7c431d21dc98E
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.9/src/capture.rs:63
   3:        0x10da95da6 - __ZN5servo4main28_$u7b$$u7b$closure$u7d$$u7d$17h75ee57e8c3524930E
                        at ports/servo/non_android_main.rs:111
   4:        0x115896d61 - __ZN3std9panicking20rust_panic_with_hook17hbc6de5ef7bb3bf80E
                        at src/libstd/panicking.rs:482
   5:        0x115801de7 - __ZN3std9panicking11begin_panic17h6b603b71cad5a3aeE
                        at /rustc/c0bbc3927e28c22edefe6a1353b5ecc95ea9a104/src/libstd/panicking.rs:412
   6:        0x110a9635d - __ZN6script3dom11eventtarget11EventTarget14dispatch_event17h98b0dcdc0b98643aE
                        at components/script/dom/eventtarget.rs:378
   7:        0x1105a4e0a - __ZN6script3dom5event5Event4fire17h8b72f900111a1cf0E
                        at components/script/dom/event.rs:241
   8:        0x1102b49d9 - __ZN6script3dom11globalscope11GlobalScope15report_an_error17hed7f363017b4a8f4E
                        at components/script/dom/globalscope.rs:440
   9:        0x10fd05f22 - __ZN6script3dom8bindings5error24report_pending_exception17he89f9aa7e1a7c974E
                        at components/script/dom/bindings/error.rs:281
  10:        0x1102b5723 - __ZN6script3dom11globalscope11GlobalScope37evaluate_script_on_global_with_result28_$u7b$$u7b$closure$u7d$$u7d$17h550fac164f0d9f8bE
                        at components/script/dom/globalscope.rs:561
  11:        0x110b0ce50 - __ZN14profile_traits4time7profile17hd7b62b2f6d581ee0E
                        at /Users/jdm/src/servo/components/profile_traits/time.rs:142
  12:        0x1102b5200 - __ZN6script3dom11globalscope11GlobalScope37evaluate_script_on_global_with_result17had1e814ac6e39528E
                        at components/script/dom/globalscope.rs:534
  13:        0x1102b4faf - __ZN6script3dom11globalscope11GlobalScope33evaluate_js_on_global_with_result17h985514dd3f00c95fE
                        at components/script/dom/globalscope.rs:513
  14:        0x110b052eb - __ZN6script3dom11userscripts11load_script28_$u7b$$u7b$closure$u7d$$u7d$17h96be5e282c4682b6E
                        at components/script/dom/userscripts.rs:42
  15:        0x10f0a0100 - __ZN4core3ops8function6FnOnce9call_once17hc3e023b3bd626068E
                        at /rustc/c0bbc3927e28c22edefe6a1353b5ecc95ea9a104/src/libcore/ops/function.rs:231
  16:        0x110b04c70 - __ZN108_$LT$script..dom..userscripts..load_script..UserScriptExecute$LT$F$GT$$u20$as$u20$script..task..TaskOnce$GT$8run_once17h8968cc4dbcd34b5bE
                        at components/script/task.rs:24
  17:        0x110a1b0df - __ZN43_$LT$T$u20$as$u20$script..task..TaskBox$GT$7run_box17h5a479c4ebf3e5550E
                        at components/script/task.rs:64
  18:        0x10f5520fb - __ZN6script3dom8document8Document32remove_script_and_layout_blocker17h90dcdc9145d6b746E
                        at components/script/dom/document.rs:2772
  19:        0x10f589007 - __ZN6script3dom4node4Node6insert17hdce7a36921274bb4E
                        at components/script/dom/node.rs:1788
  20:        0x10f588095 - __ZN6script3dom4node4Node10pre_insert17h133b41d0ec2782c6E
                        at components/script/dom/node.rs:1680
  21:        0x10f58ddcb - __ZN123_$LT$script..dom..node..Node$u20$as$u20$script..dom..bindings..codegen..Bindings..NodeBinding..NodeBinding..NodeMethods$GT$12InsertBefore17hc8908160548509bbE
                        at components/script/dom/node.rs:2219
  22:        0x10f5a2440 - __ZN6script3dom11servoparser6insert17h4b2dd6fc01580219E
                        at components/script/dom/servoparser/mod.rs:866
  23:        0x10f5a3cad - __ZN97_$LT$script..dom..servoparser..Sink$u20$as$u20$markup5ever..interface..tree_builder..TreeSink$GT$6append17h728cf0f91ecdfc3dE
                        at components/script/dom/servoparser/mod.rs:1035
  24:        0x110a0c5a6 - __ZN71_$LT$html5ever..tree_builder..TreeBuilder$LT$Handle$C$$u20$Sink$GT$$GT$9insert_at17hc20fa9efe6316beaE
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/html5ever-0.22.5/src/tree_builder/mod.rs:402
  25:        0x1109bb9e8 - __ZN71_$LT$html5ever..tree_builder..TreeBuilder$LT$Handle$C$$u20$Sink$GT$$GT$14insert_element17h7043b4c2052b4735E
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/html5ever-0.22.5/src/tree_builder/mod.rs:1201
  26:        0x1109c67c5 - __ZN71_$LT$html5ever..tree_builder..TreeBuilder$LT$Handle$C$$u20$Sink$GT$$GT$18insert_element_for17he96c26726a9fdd01E
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/html5ever-0.22.5/src/tree_builder/mod.rs:1212
  27:        0x1109da8cb - __ZN71_$LT$html5ever..tree_builder..TreeBuilder$LT$Handle$C$$u20$Sink$GT$$GT$4step17h6fec5c7a2f06fc61E
                        at /Users/jdm/src/servo/target/debug/build/html5ever-e28baae1b9a08697/out/rules.rs:52
  28:        0x1109d078c - __ZN71_$LT$html5ever..tree_builder..TreeBuilder$LT$Handle$C$$u20$Sink$GT$$GT$21process_to_completion17h97f094addcf3aeaaE
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/html5ever-0.22.5/src/tree_builder/mod.rs:314
  29:        0x1108ce5a9 - __ZN125_$LT$html5ever..tree_builder..TreeBuilder$LT$Handle$C$$u20$Sink$GT$$u20$as$u20$html5ever..tokenizer..interface..TokenSink$GT$13process_token17haf5ee2980aee9471E
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/html5ever-0.22.5/src/tree_builder/mod.rs:476
  30:        0x10f2e90af - __ZN52_$LT$html5ever..tokenizer..Tokenizer$LT$Sink$GT$$GT$13process_token17hff1a31e3644104e6E
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/html5ever-0.22.5/src/tokenizer/mod.rs:232
  31:        0x10f2ea71f - __ZN52_$LT$html5ever..tokenizer..Tokenizer$LT$Sink$GT$$GT$16emit_current_tag17hdba5dc882cfeaa8aE
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/html5ever-0.22.5/src/tokenizer/mod.rs:425
  32:        0x10f2f96d4 - __ZN52_$LT$html5ever..tokenizer..Tokenizer$LT$Sink$GT$$GT$4step17hcbd5f97db0621237E
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/html5ever-0.22.5/src/tokenizer/mod.rs:627
  33:        0x10f2ef21a - __ZN52_$LT$html5ever..tokenizer..Tokenizer$LT$Sink$GT$$GT$3run17he5b0cd1d32546f81E
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/html5ever-0.22.5/src/tokenizer/mod.rs:361
  34:        0x10f2ef3b3 - __ZN52_$LT$html5ever..tokenizer..Tokenizer$LT$Sink$GT$$GT$4feed17hacdd6de5259da615E
                        at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/html5ever-0.22.5/src/tokenizer/mod.rs:219
  35:        0x110aa51fa - __ZN6script3dom11servoparser4html9Tokenizer4feed17h78dbafc1f939df1aE
                        at components/script/dom/servoparser/html.rs:80
  36:        0x10f59f18c - __ZN6script3dom11servoparser9Tokenizer4feed17h1d5b93424b218a55E
                        at components/script/dom/servoparser/mod.rs:603
  37:        0x10f59e1fe - __ZN6script3dom11servoparser11ServoParser13do_parse_sync28_$u7b$$u7b$closure$u7d$$u7d$17hb81d65f10fcabbf4E
                        at components/script/dom/servoparser/mod.rs:481
  38:        0x10f59e8d4 - __ZN6script3dom11servoparser11ServoParser8tokenize17h9d811b77a783c336E
                        at components/script/dom/servoparser/mod.rs:519
  39:        0x10f59dfb4 - __ZN6script3dom11servoparser11ServoParser13do_parse_sync17h1978751f79a30cb3E
                        at components/script/dom/servoparser/mod.rs:481
  40:        0x10f59dcb7 - __ZN6script3dom11servoparser11ServoParser10parse_sync28_$u7b$$u7b$closure$u7d$$u7d$17he38993c442cb81f2E
                        at components/script/dom/servoparser/mod.rs:463
  41:        0x110b09b36 - __ZN14profile_traits4time7profile17h6bbfd6b50f7c1f69E
                        at /Users/jdm/src/servo/components/profile_traits/time.rs:142
  42:        0x10f59dc22 - __ZN6script3dom11servoparser11ServoParser10parse_sync17h6353cd48e59a3f59E
                        at components/script/dom/servoparser/mod.rs:455
  43:        0x10f5a0b4d - __ZN93_$LT$script..dom..servoparser..ParserContext$u20$as$u20$net_traits..FetchResponseListener$GT$16process_response17ha43dca92ce23795eE
                        at components/script/dom/servoparser/mod.rs:750
  44:        0x110010e1d - __ZN6script13script_thread12ScriptThread21handle_fetch_metadata17h6f54c6ea768efb39E
                        at components/script/script_thread.rs:3274
  45:        0x10fff8e41 - __ZN6script13script_thread12ScriptThread29handle_msg_from_constellation17h270c107535deee62E
                        at components/script/script_thread.rs:1551
  46:        0x10fff2f23 - __ZN6script13script_thread12ScriptThread11handle_msgs28_$u7b$$u7b$closure$u7d$$u7d$17h55be7dc697aa892cE
                        at components/script/script_thread.rs:1287
  47:        0x10fff40b0 - __ZN6script13script_thread12ScriptThread13profile_event17h04c85c8e85b7faf1E
                        at components/script/script_thread.rs:1522
  48:        0x10fff1005 - __ZN6script13script_thread12ScriptThread11handle_msgs17hf2605c765025ae5eE
                        at components/script/script_thread.rs:1281
  49:        0x10ffee9dc - __ZN6script13script_thread12ScriptThread5start17h94b723799d378f58E
                        at components/script/script_thread.rs:1126
  50:        0x10ffe9ed4 - __ZN90_$LT$script..script_thread..ScriptThread$u20$as$u20$script_traits..ScriptThreadFactory$GT$6create28_$u7b$$u7b$closure$u7d$$u7d$28_$u7b$$u7b$closure$u7d$$u7d$17he40682aa2d217f4eE
                        at components/script/script_thread.rs:711
  51:        0x1108cfbca - __ZN14profile_traits3mem12ProfilerChan25run_with_memory_reporting17haa007d7001100c18E
                        at /Users/jdm/src/servo/components/profile_traits/mem.rs:88
  52:        0x10ffea4c9 - __ZN90_$LT$script..script_thread..ScriptThread$u20$as$u20$script_traits..ScriptThreadFactory$GT$6create28_$u7b$$u7b$closure$u7d$$u7d$17ha8ed87fc7bf3647cE
                        at components/script/script_thread.rs:709
  53:        0x1108d1772 - __ZN3std10sys_common9backtrace28__rust_begin_short_backtrace17h159dc492e0c540f4E
                        at /rustc/c0bbc3927e28c22edefe6a1353b5ecc95ea9a104/src/libstd/sys_common/backtrace.rs:135
  54:        0x10fbd3a12 - __ZN3std6thread7Builder15spawn_unchecked28_$u7b$$u7b$closure$u7d$$u7d$28_$u7b$$u7b$closure$u7d$$u7d$17h5addcaac0c8a7d49E
                        at /rustc/c0bbc3927e28c22edefe6a1353b5ecc95ea9a104/src/libstd/thread/mod.rs:469
  55:        0x1100f90a2 - __ZN101_$LT$std..panic..AssertUnwindSafe$LT$F$GT$$u20$as$u20$core..ops..function..FnOnce$LT$$LP$$RP$$GT$$GT$9call_once17hdf57eb7152b73189E
                        at /rustc/c0bbc3927e28c22edefe6a1353b5ecc95ea9a104/src/libstd/panic.rs:309
  56:        0x10e605402 - __ZN3std9panicking3try7do_call17h30150fe65cb52bf6E
                        at /rustc/c0bbc3927e28c22edefe6a1353b5ecc95ea9a104/src/libstd/panicking.rs:297
  57:        0x11589fc7e - ___rust_maybe_catch_panic
                        at src/libpanic_unwind/lib.rs:92
  58:        0x10e5dd7c4 - __ZN3std9panicking3try17hf5941656f56e489fE
                        at /rustc/c0bbc3927e28c22edefe6a1353b5ecc95ea9a104/src/libstd/panicking.rs:276
  59:        0x1102007f2 - __ZN3std5panic12catch_unwind17hf68911bf6247c6e1E
                        at /rustc/c0bbc3927e28c22edefe6a1353b5ecc95ea9a104/src/libstd/panic.rs:388
  60:        0x10fbd14fb - __ZN3std6thread7Builder15spawn_unchecked28_$u7b$$u7b$closure$u7d$$u7d$17h238313f64b2796deE
                        at /rustc/c0bbc3927e28c22edefe6a1353b5ecc95ea9a104/src/libstd/thread/mod.rs:468
  61:        0x10fbeb273 - __ZN50_$LT$F$u20$as$u20$alloc..boxed..FnBox$LT$A$GT$$GT$8call_box17h721c49a0aa678011E
                        at /rustc/c0bbc3927e28c22edefe6a1353b5ecc95ea9a104/src/liballoc/boxed.rs:724
  62:        0x11589f22b - __ZN3std3sys4unix6thread6Thread3new12thread_start17hc651d155b46de6bdE
                        at src/libstd/sys_common/thread.rs:14
  63:     0x7fffae9ec93a - __pthread_body
  64:     0x7fffae9ec886 - __pthread_start