--- a/testing/web-platform/tests/tools/wptrunner/wptrunner/browsers/firefox.py
+++ b/testing/web-platform/tests/tools/wptrunner/wptrunner/browsers/firefox.py
@@ -1,15 +1,14 @@
 import json
 import os
 import platform
 import signal
 import subprocess
 import sys
-import tempfile
 
 import mozinfo
 import mozleak
 from mozprocess import ProcessHandler
 from mozprofile import FirefoxProfile, Preferences
 from mozrunner import FirefoxRunner
 from mozrunner.utils import test_environment, get_stack_fixer_function
 from mozcrash import mozcrash
@@ -224,18 +223,18 @@ class FirefoxBrowser(Browser):
                                       "dom.send_after_paint_to_content": True,
                                       "network.preload": True})
         if self.e10s:
             self.profile.set_preferences({"browser.tabs.remote.autostart": True})
 
         if self.test_type == "reftest":
             self.profile.set_preferences({"layout.interruptible-reflow.enabled": False})
 
-        if self.leak_check and kwargs.get("check_leaks", True):
-            self.leak_report_file = os.path.join(self.profile.profile, "runtests_leaks.log")
+        if self.leak_check:
+            self.leak_report_file = os.path.join(self.profile.profile, "runtests_leaks_%s.log" % os.getpid())
             if os.path.exists(self.leak_report_file):
                 os.remove(self.leak_report_file)
             env["XPCOM_MEM_BLOAT_LOG"] = self.leak_report_file
         else:
             self.leak_report_file = None
 
         # Bug 1262954: winxp + e10s, disable hwaccel
         if (self.e10s and platform.system() in ("Windows", "Microsoft") and
@@ -299,16 +298,17 @@ class FirefoxBrowser(Browser):
                     if not force or not clean:
                         retcode = stop_f()
                         if retcode is not None:
                             self.logger.info("Browser exited with return code %s" % retcode)
                             break
             except OSError:
                 # This can happen on Windows if the process is already dead
                 pass
+        self.process_leaks()
         self.logger.debug("stopped")
 
     def process_leaks(self):
         self.logger.debug("PROCESS LEAKS %s" % self.leak_report_file)
         if self.lsan_handler:
             self.lsan_handler.process()
         if self.leak_report_file is not None:
             mozleak.process_leak_log(
@@ -348,19 +348,18 @@ class FirefoxBrowser(Browser):
                                            data,
                                            command=" ".join(self.runner.command))
 
     def is_alive(self):
         if self.runner:
             return self.runner.is_running()
         return False
 
-    def cleanup(self):
-        self.stop()
-        self.process_leaks()
+    def cleanup(self, force=False):
+        self.stop(force)
 
     def executor_browser(self):
         assert self.marionette_port is not None
         return ExecutorBrowser, {"marionette_port": self.marionette_port}
 
     def check_for_crashes(self):
         dump_dir = os.path.join(self.profile.profile, "minidumps")