Adding version decorator to pingback test

Bug: 
Change-Id: I29b9c78a9e23afa819fe7d4ebf96ede206a1ac91
Reviewed-on: https://chromium-review.googlesource.com/661577Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501304}

tools/chrome_proxy/webdriver/smoke.py

@@ -83,7 +83,7 @@ class Smoke(IntegrationTest):
       self.assertEqual(1, succeeded['count'])
 
   # Ensure pageload metric pingback with DataSaver has the variations header.
-  # Disabled on android because the net log is not copied yet. crbug.com/761507
+  @ChromeVersionEqualOrAfterM(62)
   def testPingbackHasVariations(self):
     with TestDriver() as t:
       t.AddChromeArg('--enable-spdy-proxy-auth')