Create a tab upon creation of a fake browser instance.

telemetry/telemetry/testing/fakes/__init__.py

Index: telemetry/telemetry/testing/fakes/__init__.py
diff --git a/telemetry/telemetry/testing/fakes/__init__.py b/telemetry/telemetry/testing/fakes/__init__.py
index 41dd87a96a245f8b7613bb59101a381dde38721b..9e345fcff8b7701dfb2d61fb728979c4a79806cc 100644
--- a/telemetry/telemetry/testing/fakes/__init__.py
+++ b/telemetry/telemetry/testing/fakes/__init__.py
@@ -192,6 +192,8 @@ def CreateBrowserFinderOptions(browser_type=None):
 class _FakeBrowser(object):
   def __init__(self, platform):
     self._tabs = _FakeTabList(self)
+    # Fake the creation of the first tab.
+    self._tabs.New()
     self._returned_system_info = FakeSystemInfo()
     self._platform = platform
     self._browser_type = 'release'