Support for figuring out the number of contexts in a page.

tools/telemetry/telemetry/core/web_contents.py

Index: tools/telemetry/telemetry/core/web_contents.py
diff --git a/tools/telemetry/telemetry/core/web_contents.py b/tools/telemetry/telemetry/core/web_contents.py
index c5137679de7a383edfe192a8c4eb1089f242cba7..e4360179947e673500499461e736c07f61e66626 100644
--- a/tools/telemetry/telemetry/core/web_contents.py
+++ b/tools/telemetry/telemetry/core/web_contents.py
@@ -123,6 +123,11 @@ class WebContents(object):
     return self._inspector_backend.EvaluateJavaScript(
         expr, context_id=context_id, timeout=timeout)
 
+  def EnableAllContexts(self):
+    """Enable all contexts in a page. Returns the number of available contexts.
+    """
+    return self._inspector_backend.EnableAllContexts()
+
   @property
   def message_output_stream(self):
     return self._inspector_backend.message_output_stream