Adding a probe fallback to HTTP test

tools/chrome_proxy/webdriver/common.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import argparse
 import json
 import logging
 import os
 import re
 import socket
@@ skipping 309 matching lines @@
     Behavior is analogous to 'function(){ return <script> }();'
 
     Args:
       script: A string of Javascript code.
       timeout: Timeout for the Javascript code to return in seconds.
     Returns:
       A string of the verbatim output from the Javascript execution.
     """
     return self.ExecuteJavascript("return " + script, timeout)
 
-  def GetHistogram(self, histogram):
+  def GetHistogram(self, histogram, timeout=30):
+    """Gets a Chrome histogram as a dictionary object.
+
+    Args:
+      histogram: the name of the histogram to fetch
+      timeout: timeout for the underlying Javascript query.
+
+    Returns:
+      A dictionary object containing information about the histogram.
+    """
     js_query = 'statsCollectionController.getBrowserHistogram("%s")' % histogram
-    string_response = self.ExecuteJavascriptStatement(js_query)
+    string_response = self.ExecuteJavascriptStatement(js_query, timeout)
     self._logger.debug('Got %s histogram=%s', histogram, string_response)
     return json.loads(string_response)
 
   def WaitForJavascriptExpression(self, expression, timeout, min_poll=0.1,
       max_poll=1):
     """Waits for the given Javascript expression to evaluate to True within the
     given timeout. This method polls the Javascript expression within the range
     of |min_poll| and |max_poll|.
 
     Args:
@@ skipping 32 matching lines @@
     for log in self._driver.execute('getLog', {'type': 'performance'})['value']:
       message = json.loads(log['message'])['message']
       self._logger.debug('Got Performance log: %s', log['message'])
       if re.match(method_filter, message['method']):
         all_messages.append(message)
     self._logger.info('Got %d performance logs with filter method=%s',
       len(all_messages), method_filter)
     self._has_logs = False
     return all_messages
 
+  def SleepUntilHistogramHasEntry(self, histogram_name, sleep_intervals=10):
+    """Polls if a histogram exists in 1-6 second intervals for 10 intervals.
+    Allows script to run with a timeout of 5 seconds, so the default behavior
+    allows up to 60 seconds until timeout.
+
+    Args:
+      histogram_name: The name of the histogram to wait for
+      sleep_intervals: The number of polling intervals, each polling cycle takes
+      no more than 6 seconds.
+    Returns:
+      Whether the histogram exists
+    """
+    histogram = {}
+    while(not histogram and sleep_intervals > 0):
+      histogram = self.GetHistogram(histogram_name, 5)
+      if (not histogram):
+        time.sleep(1)
+        sleep_intervals -= 1
+
+    return bool(histogram)
+
   def GetHTTPResponses(self, include_favicon=False, skip_domainless_pages=True):
     """Parses the Performance Logs and returns a list of HTTPResponse objects.
 
     Use caution when calling this function  multiple times. Only responses
     since the last time this function was called are returned (or since Chrome
     started, whichever is later). An Exception will be raised if no page was
     loaded since the last time this function was called.
 
     Args:
       include_favicon: A bool that if True will include responses for favicons.
@@ skipping 247 matching lines @@
       args[0].skipTest('This test runs on Mac OS only.')
   return wrapper
 
 def NotMac(func):
   def wrapper(*args, **kwargs):
     if sys.platform == 'darwin':
       func(*args, **kwargs)
     else:
       args[0].skipTest('This test does not run on Mac OS.')
   return wrapper