Do not run pingback webdriver tests M >=79

Bug: 990083
Change-Id: I8d3ac999d517cd4ed56245150a4bba6c576291d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1815589
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Auto-Submit: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698513}

tools/chrome_proxy/webdriver/https_previews.py

@@ -11,6 +11,7 @@ from common import TestDriver
 from common import IntegrationTest
 from decorators import AndroidOnly
 from decorators import ChromeVersionEqualOrAfterM
+from decorators import ChromeVersionBeforeM
 
 from selenium.common.exceptions import TimeoutException
 
@@ -153,6 +154,7 @@ class HttpsPreviewsBaseClass():
 
   # Verifies that a Lite Page pageload sends a DRP pingback.
   @ChromeVersionEqualOrAfterM(74)
+  @ChromeVersionBeforeM(79)
   def testPingbackSent(self):
     with TestDriver() as t:
       t.AddChromeArg('--enable-data-reduction-proxy-force-pingback')

tools/chrome_proxy/webdriver/smoke.py

@@ -71,6 +71,7 @@ class Smoke(IntegrationTest):
       self.assertGreater(num_chrome_proxy_request_headers, 0)
 
   # Ensure pageload metric pingback with DataSaver.
+  @ChromeVersionBeforeM(79)
   def testPingback(self):
     with TestDriver() as t:
       t.AddChromeArg('--enable-spdy-proxy-auth')
@@ -87,6 +88,7 @@ class Smoke(IntegrationTest):
 
   # Ensure pageload metric pingback with DataSaver has the variations header.
   @ChromeVersionEqualOrAfterM(62)
+  @ChromeVersionBeforeM(79)
   def testPingbackHasVariations(self):
     with TestDriver() as t:
       t.AddChromeArg('--enable-spdy-proxy-auth')