Created attachment 8787002 [details] valgrind.txt User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:48.0) Gecko/20100101 Firefox/48.0 Build ID: 20160728203720 Steps to reproduce: Wrote a program which creates, uses and destroys a JSRuntime and JSContext on a thread which is not the main thread. Profiled that program (unit test runner) with Valgrind. Actual results: A small leak was observed: see attached valgrind.txt. The leak does not occur when equivalent code runs only on the main thread. In fact the attached Valgrind report comes from a program which creates and destroys at least a dozen JSRuntimes on the main thread. Expected results: Valgrind should not report any leaked memory.
This looks like it is a leak involving an embedding of the SpiderMonkey engine, and we focus on Firefox in particular in MemShrink.