+++ This bug was initially created as a clone of Bug #780594 +++ We saw this on inbound a couple times yesterday. https://tbpl.mozilla.org/php/getParsedLog.php?id=20231691&tree=Mozilla-Inbound 13:31:10 INFO - TEST-START | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js 13:31:10 INFO - TEST-PASS | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | home button present 13:31:11 INFO - TEST-PASS | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | domwindow.document.location.href: chrome://global/content/commonDialog.xul 13:31:11 INFO - TEST-INFO | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | Console message: OpenGL LayerManager Initialized Succesfully. 13:31:11 INFO - Version: 2.1 NVIDIA-1.6.36 13:31:11 INFO - Vendor: NVIDIA Corporation 13:31:11 INFO - Renderer: NVIDIA GeForce 320M OpenGL Engine 13:31:11 INFO - FBO Texture Target: TEXTURE_2D 13:31:11 INFO - TEST-PASS | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | dialog appeared in response to home button drop 13:31:11 WARNING - TEST-UNEXPECTED-FAIL | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | uncaught exception - NS_ERROR_FAILURE: Failure at chrome://browser/content/browser.js:7183 13:31:11 WARNING - This is a harness error. 13:31:11 INFO - Stack trace: 13:31:11 INFO - JS frame :: chrome://mochikit/content/tests/SimpleTest/SimpleTest.js :: simpletestOnerror :: line 1105 13:31:11 INFO - native frame :: <unknown filename> :: <TOP_LEVEL> :: line 0 13:31:11 INFO - TEST-INFO | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | Console message: [JavaScript Error: "NS_ERROR_FAILURE: Failure" {file: "chrome://browser/content/browser.js" line: 7183}] 13:31:11 INFO - TEST-INFO | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | Attempting second drop, of a javascript: URI 13:31:11 INFO - TEST-PASS | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | expected uncaught exception 13:31:11 INFO - TEST-INFO | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | Console message: [JavaScript Error: "NS_ERROR_DOM_BAD_URI: Access to restricted URI denied" {file: "resource://gre/components/contentAreaDropListener.js" line: 91}] 13:31:11 INFO - TEST-PASS | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | drop was blocked 13:31:11 INFO - INFO TEST-END | chrome://mochitests/content/browser/browser/base/content/test/browser_homeDrop.js | finished in 1019ms

Probably a regression from bug 841350, which reverted (?) the fix for bug 780594. I have a pile of fuzz testcases that reproduce this error reliably on my machine. The only thing they have in common is a call to gcslice.

I guess it would be best to revert bug 841350 and then fix it better. Jesse - can you post one or two of those testcases so I have something to test against to make sure this doesn't happen again?

Fixed by bug 841350 backout. https://hg.mozilla.org/mozilla-central/rev/aceda400d212

It would take me a while to extract a small testcase, and it wouldn't be easy to translate into an automated test because it would need to call gcslice. When this bug was present, my fuzzer hit it pretty often. So I'll notice if it happens again.