Try to enable root when starting adb, as root is needed for a full coverage.

BUG=375178
R=tonyg@chromium.org

Review URL: https://codereview.chromium.org/294943002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271680 0039d316-1c4b-4281-b951-d872f2087c98

tools/telemetry/telemetry/core/backends/chrome/android_browser_finder.py

@@ -199,6 +199,10 @@ def FindAllAvailableBrowsers(finder_options, logging=real_logging):
   device = devices[0]
 
   adb = adb_commands.AdbCommands(device=device)
+  # Trying to root the device, if possible.
+  if not adb.IsRootEnabled():
+    # Ignore result.
+    adb.EnableAdbRoot()
 
   if sys.platform.startswith('linux'):
     # Host side workaround for crbug.com/268450 (adb instability)