Use a blocking queue.get() to get browser test results. NFC (#20848)

Author: sbc100

test/common.py

@@ -28,6 +28,7 @@
 import time
 import webbrowser
 import unittest
+import queue
 
 import clang_native
 import jsrun
@@ -1956,25 +1957,21 @@ def run_browser(self, html_file, expected=None, message=None, timeout=None, extr
           'http://localhost:%s/%s' % (self.port, html_file),
           self.get_dir()
         ))
-        received_output = False
-        output = '[no http server activity]'
-        start = time.time()
         if timeout is None:
           timeout = self.browser_timeout
-        while time.time() - start < timeout:
-          if not self.harness_out_queue.empty():
-            output = self.harness_out_queue.get()
-            received_output = True
-            break
-          time.sleep(0.1)
-        if not received_output:
+        try:
+          output = self.harness_out_queue.get(block=True, timeout=timeout)
+        except queue.Empty:
           BrowserCore.unresponsive_tests += 1
           print('[unresponsive tests: %d]' % BrowserCore.unresponsive_tests)
           self.browser_restart()
+          # Rather than fail the test here, let fail on the `assertContained` so
+          # that the test can be retried via `extra_tries`
+          output = '[no http server activity]'
         if output is None:
           # the browser harness reported an error already, and sent a None to tell
           # us to also fail the test
-          raise Exception('failing test due to browser harness error')
+          self.fail('browser harness error')
         if output.startswith('/report_result?skipped:'):
           self.skipTest(unquote(output[len('/report_result?skipped:'):]).strip())
         else: