[Telemetry] Add labels attribute to page as the new way to set label

tools/telemetry/telemetry/page/__init__.py

Index: tools/telemetry/telemetry/page/__init__.py
diff --git a/tools/telemetry/telemetry/page/__init__.py b/tools/telemetry/telemetry/page/__init__.py
index 4352e41ba0d82cda6e577333f0579fe75d77d97f..df68c7b5566fb6219cf8ac5cb423739e78046416 100644
--- a/tools/telemetry/telemetry/page/__init__.py
+++ b/tools/telemetry/telemetry/page/__init__.py
@@ -23,7 +23,7 @@ def _UpdateCredentials(credentials_path):
 
 class Page(user_story.UserStory):
   def __init__(self, url, page_set=None, base_dir=None, name='',
-               credentials_path=None):
+               credentials_path=None, labels=None):
     super(Page, self).__init__(name)
     self._url = url
     self._page_set = page_set
@@ -40,6 +40,11 @@ class Page(user_story.UserStory):
         logging.error('Invalid credentials path: %s' % credentials_path)
         credentials_path = None
     self._credentials_path = credentials_path
+    if labels is None:
+      labels = set([])
+    elif isinstance(labels, list):
+      labels = set(labels)
+    self._labels = labels
 
     # These attributes can be set dynamically by the page.
     self.synthetic_delays = dict()
@@ -49,6 +54,11 @@ class Page(user_story.UserStory):
     self.script_to_evaluate_on_commit = None
     self._SchemeErrorCheck()
 
+
+  @property
+  def labels(self):
+    return self._labels
+
   @property
   def credentials_path(self):
     return self._credentials_path