[Affected versions]: Nightly 56.0a1 [Affected platforms]: Platforms: Windows 10 x 64, Mac OS X 10.12 [Steps to reproduce]: 1. Go to https://duckduckgo.com/ 2. Open Debugger. 3. Navigate to a file that has ".js" termination (I used d2190.js) 4. Press CTRL + F or CMD + F 5. Write something In the search field. I wrote "data" [Expected result]: Word "data" should be displayed as a search result. [Actual result]: I received a "Warning: Unresponsive script" [Note]: This issue is also reproducible with www.yahoo.com

Able to reproduce, stop script error is here: Script: chrome://devtools/content/sour…odemirror/codemirror.bundle.js:1799

Here's the callstack for the error TypeError: tabForEvent is null[Learn More] tabbrowser.xml:5687:1 onxblDOMWillOpenModalDialog chrome://browser/content/tabbrowser.xml:5687:1 openModalWindow jar:file:///Applications/FirefoxNightly.app/Contents/Resources/omni.ja!/components/nsPrompter.js:363:5 openPrompt jar:file:///Applications/FirefoxNightly.app/Contents/Resources/omni.ja!/components/nsPrompter.js:573:9 confirmEx jar:file:///Applications/FirefoxNightly.app/Contents/Resources/omni.ja!/components/nsPrompter.js:714:9 [Symbol.match] self-hosted:3978:1 match self-hosted:4749:13 CodeMirror</</StringStream.prototype.match chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:1799:18 token resource://devtools/client/debugger/new/debugger.js:17633:16 readToken chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:1955:18 runMode chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:2012:35 loop chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:1869:6 highlightLine chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:1892:55 getLineStyles chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:1902:19 buildLineContent chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:2148:39 getLineContent chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:2526:11 buildLineElement chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:2607:16 patchDisplay chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:4523:19 updateDisplayIfNeeded chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:4431:4 endOperation_W1 chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:3991:41 endOperations chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:3968:8 endOperation/< chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:3957:6 finishOperation chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:2438:6 endOperation chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:3954:4 runInOp chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:4083:14 operation chrome://devtools/content/sourceeditor/codemirror/codemirror.bundle.js:8587:36 doSearch resource://devtools/client/debugger/new/debugger.js:17692:11 find resource://devtools/client/debugger/new/debugger.js:17803:11 searchContents/< resource://devtools/client/debugger/new/debugger.js:25330:21 next self-hosted:1183:9 step resource://devtools/client/debugger/new/debugger.js:25099:184 step/< resource://devtools/client/debugger/new/debugger.js:25099:362

Tracking this here: https://github.com/devtools-html/debugger.html/issues/3460

This should now be resolved on nightly.

It was fixed with this release: https://bugzilla.mozilla.org/show_bug.cgi?id=1385421

I have just retested this issue and the problem is still there. I can still reproduce this on the systems mentioned in the description. Tested with the latest Nightly 56.0a1(2017-07-31)

I'm able to reproduce this as well using the same steps.

This was fixed here: https://bugzilla.mozilla.org/show_bug.cgi?id=1399673