[chromedriver] Use snapshot instead of continuous archive, drop M48 and add M51.

chrome/test/chromedriver/test/run_all_tests.py

Index: chrome/test/chromedriver/test/run_all_tests.py
diff --git a/chrome/test/chromedriver/test/run_all_tests.py b/chrome/test/chromedriver/test/run_all_tests.py
index c40ad8651304edff1fa1ee2296f581e807a5f51c..9bb92768e4092c6e09bd1d2717e2ef483fc81c4d 100755
--- a/chrome/test/chromedriver/test/run_all_tests.py
+++ b/chrome/test/chromedriver/test/run_all_tests.py
@@ -191,15 +191,15 @@ def main():
     latest_snapshot_revision = archive.GetLatestSnapshotVersion()
     versions = [
         ['HEAD', latest_snapshot_revision],
+        ['51', archive.CHROME_51_REVISION],
         ['50', archive.CHROME_50_REVISION],
         ['49', archive.CHROME_49_REVISION],
-        ['48', archive.CHROME_48_REVISION],
     ]
     code = 0
     for version in versions:
       if options.chrome_version and version[0] != options.chrome_version:
         continue
-      download_site = archive.Site.CONTINUOUS
+      download_site = archive.Site.CHROMIUM_SNAPSHOT
       version_name = version[0]
       if version_name == 'HEAD':
         version_name = version[1]