[telemetry] Simplify the way PageRunner is called.

tools/telemetry/telemetry/core/browser.py

Index: tools/telemetry/telemetry/core/browser.py
diff --git a/tools/telemetry/telemetry/core/browser.py b/tools/telemetry/telemetry/core/browser.py
index 09d37445c306b8f2128c9a7149634ea71b078246..daabd1be17400e1a8f4e7a8ad529fa6637cd557e 100644
--- a/tools/telemetry/telemetry/core/browser.py
+++ b/tools/telemetry/telemetry/core/browser.py
@@ -242,23 +242,26 @@ class Browser(object):
     return self._http_server
 
   def SetHTTPServerDirectories(self, paths):
+    """Returns True if the HTTP server was started, False otherwise."""
     if not isinstance(paths, list):
       paths = [paths]
     paths = [os.path.abspath(p) for p in paths]
 
     if paths and self._http_server and self._http_server.paths == paths:
-      return
+      return False
 
     if self._http_server:
       self._http_server.Close()
       self._http_server = None
 
     if not paths:
-      return
+      return False
 
     self._http_server = temporary_http_server.TemporaryHTTPServer(
       self._browser_backend, paths)
 
+    return True
+
   def SetReplayArchivePath(self, archive_path, append_to_existing_wpr=False):
     if self._wpr_server:
       self._wpr_server.Close()