Bug 1899781 - Use correct timeout in xpcshell TV r=jmaher

harness_timeout should be assigned to kwargs for it to have any effect.

... and fix the exponential backoff waiter, to wait for at most 15
seconds between checks. Otherwise a timed-out test could be kept
running for several minutes longer, which is a waste of time.

Differential Revision: https://phabricator.services.mozilla.com/D212124

testing/xpcshell/remotexpcshelltests.py

@@ -123,6 +123,9 @@ class RemoteProcessMonitor(object):
             time.sleep(interval)
             timer += interval
             interval *= 1.5
+            # We're using exponential back-off. To avoid unnecessarily waiting
+            # for too long, cap the maximum sleep interval to 15 seconds.
+            interval = min(15, interval)
             if timeout and timer > timeout:
                 status = False
                 self.log.info(

testing/xpcshell/runxpcshelltests.py

@@ -2036,7 +2036,7 @@ class XPCShellTests(object):
                 sequential_tests = []
                 self.env["MOZ_CHAOSMODE"] = "0xfb"
                 # chaosmode runs really slow, allow tests extra time to pass
-                self.harness_timeout = self.harness_timeout * 2
+                kwargs["harness_timeout"] = self.harness_timeout * 2
                 for i in range(VERIFY_REPEAT):
                     self.testCount += 1
                     test = testClass(
@@ -2046,7 +2046,7 @@ class XPCShellTests(object):
                 status = self.runTestList(
                     tests_queue, sequential_tests, testClass, mobileArgs, **kwargs
                 )
-                self.harness_timeout = self.harness_timeout / 2
+                kwargs["harness_timeout"] = self.harness_timeout
                 return status
 
             steps = [