[telemetry] Sort imports in Telemetry and its dependents.

tools/telemetry/telemetry/core/tab_unittest.py

 # Copyright 2012 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 logging
 import tempfile
 
+from telemetry.core import exceptions
+from telemetry.core.platform import tracing_category_filter
+from telemetry.core.platform import tracing_options
+from telemetry.core import util
+from telemetry.core import video
 from telemetry import decorators
 from telemetry.image_processing import image_util
 from telemetry.image_processing import rgba_color
-from telemetry.core import exceptions
-from telemetry.core import util
-from telemetry.core import video
-from telemetry.core.platform import tracing_category_filter
-from telemetry.core.platform import tracing_options
 from telemetry.timeline import model
 from telemetry.unittest_util import tab_test_case
 
 
 def _IsDocumentVisible(tab):
   return not tab.EvaluateJavaScript('document.hidden || document.webkitHidden')
 
 
 class FakePlatformBackend(object):
   def __init__(self):
@@ skipping 169 matching lines @@
     assert screenshot is not None
     image_util.GetPixelColor(
         screenshot, 0 * pixel_ratio, 0 * pixel_ratio).AssertIsRGB(
             0, 255, 0, tolerance=2)
     image_util.GetPixelColor(
         screenshot, 31 * pixel_ratio, 31 * pixel_ratio).AssertIsRGB(
             0, 255, 0, tolerance=2)
     image_util.GetPixelColor(
         screenshot, 32 * pixel_ratio, 32 * pixel_ratio).AssertIsRGB(
             255, 255, 255, tolerance=2)