Update failing webdriver tests with decorators/updates

-Video.testVideoMetrics - A new version of ffmpeg changed the duration of the test video by 0.004 seconds.  The dev team confirmed this is fine.  Updating the expected value.  Also changing the level of variance to 0.01 so this is less brittle in the future.
-Smoke.testPageID - Add a >=59 decorator as this tests is only applicable for M59+
-LitePage.testLitePageNotAcceptedForCellularOnlyFlag - Add a >=61 decorator as this tests is only applicable for M61+

Bug: 740668,740670
Change-Id: Ib6fcdfa80f57eee195c09d21fc36157e7259bd3f
Reviewed-on: https://chromium-review.googlesource.com/565627
Commit-Queue: Richard Bustamante <bustamante@google.com>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Reviewed-by: Scott Little <sclittle@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486083}

tools/chrome_proxy/webdriver/lite_page.py

@@ -98,6 +98,7 @@ class LitePage(IntegrationTest):
 
   # Checks that a Lite Page is not served for the Cellular-Only option but
   # not on cellular connection.
+  @ChromeVersionEqualOrAfterM(61)
   def testLitePageNotAcceptedForCellularOnlyFlag(self):
     with TestDriver() as test_driver:
       test_driver.AddChromeArg('--enable-spdy-proxy-auth')

tools/chrome_proxy/webdriver/smoke.py

@@ -7,6 +7,7 @@ import time
 from common import TestDriver
 from common import IntegrationTest
 from decorators import NotAndroid
+from decorators import ChromeVersionEqualOrAfterM
 
 
 class Smoke(IntegrationTest):
@@ -101,6 +102,7 @@ class Smoke(IntegrationTest):
         self.assertEqual(200, response.status)
 
   # Verify unique page IDs are sent in the Chrome-Proxy header.
+  @ChromeVersionEqualOrAfterM(59)
   def testPageID(self):
     with TestDriver() as t:
       t.AddChromeArg('--enable-spdy-proxy-auth')

tools/chrome_proxy/webdriver/video.py

@@ -52,7 +52,7 @@ class Video(IntegrationTest):
   @Slow
   def testVideoMetrics(self):
     expected = {
-      'duration': 3.124,
+      'duration': 3.128,
       'webkitDecodedFrameCount': 54.0,
       'videoWidth': 1280.0,
       'videoHeight': 720.0
@@ -81,7 +81,7 @@ class Video(IntegrationTest):
           'document.querySelectorAll("video")[0].%s' % metric))
         self.assertAlmostEqual(expected[metric], actual, msg="Compressed video "
           "metric doesn't match expected! Metric=%s Expected=%f Actual=%f"
-          % (metric, expected[metric], actual), places=None, delta=0.001)
+          % (metric, expected[metric], actual), places=None, delta=0.01)
 
   # Check that the compressed video can be seeked. Use a slow network to ensure
   # the entire video isn't downloaded before we have a chance to seek.