[telemetry] Support absolute paths by changing file:/// to file://. More robust file path handling.

content/test/gpu/gpu_tests/webgl_robustness.py

 # Copyright 2013 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.
 from telemetry import test
 from telemetry.page import page_set
 from webgl_conformance import WebglConformanceValidator
 from webgl_conformance import conformance_harness_script
 from webgl_conformance import conformance_path
 
 
@@ skipping 37 matching lines @@
   enabled = False
   test = WebglConformanceValidator
 
   def CreatePageSet(self, options):
     page_set_dict = {
       'description': 'Test cases for WebGL robustness',
       'user_agent_type': 'desktop',
       'serving_dirs': [''],
       'pages': [
         {
-          'url': 'file:///extra/lots-of-polys-example.html',
+          'url': 'file://extra/lots-of-polys-example.html',
           'script_to_evaluate_on_commit': robustness_harness_script,
           'navigate_steps': [
             { 'action': 'navigate' },
             { 'action': 'wait', 'javascript': 'webglTestHarness._finished' }
           ]
         }
       ]
     }
     return page_set.PageSet.FromDict(page_set_dict, conformance_path)