Bug 1486568 - forceNewProcess option from BrowserTestUtils should ensure that a cached process is not reused. r=mconley

testing/mochitest/BrowserTestUtils/BrowserTestUtils.jsm

@@ -186,6 +186,7 @@ var BrowserTestUtils = {
       // If DEFAULT_PROCESSSELECTOR_CID is null, we're in non-e10s mode and we
       // should skip this.
       if (options.forceNewProcess && DEFAULT_PROCESSSELECTOR_CID) {
+        Services.ppmm.releaseCachedProcesses();
         registrar.registerFactory(OUR_PROCESSSELECTOR_CID, "",
                                   PROCESSSELECTOR_CONTRACTID, null);
       }