Fix for extension binding race condition when evaluating JS.

tools/telemetry/telemetry/core/extension_unittest.py

Index: tools/telemetry/telemetry/core/extension_unittest.py
diff --git a/tools/telemetry/telemetry/core/extension_unittest.py b/tools/telemetry/telemetry/core/extension_unittest.py
index b15fd9988440bd7ff1ce10871101b0b23d20d1c1..1b330216b121dc5c23ffeaa62836d09c78eab4be 100644
--- a/tools/telemetry/telemetry/core/extension_unittest.py
+++ b/tools/telemetry/telemetry/core/extension_unittest.py
@@ -44,6 +44,8 @@ class ExtensionTest(unittest.TestCase):
       logging.warning('Did not find a browser that supports extensions, '
                       'skipping test.')
       return
+    self.assertTrue(
+        self._extension.EvaluateJavaScript('chrome.runtime != null'))
     self._extension.ExecuteJavaScript('setTestVar("abcdef")')
     self.assertEquals('abcdef',
                       self._extension.EvaluateJavaScript('_testVar'))
@@ -125,6 +127,8 @@ class MultipleExtensionTest(unittest.TestCase):
     for load_extension in self._extensions_to_load:
       extension = self._browser.extensions[load_extension]
       assert extension
+      self.assertTrue(
+          extension.EvaluateJavaScript('chrome.runtime != null'))
       extension.ExecuteJavaScript('setTestVar("abcdef")')
       self.assertEquals('abcdef', extension.EvaluateJavaScript('_testVar'))
 
@@ -147,6 +151,8 @@ class ComponentExtensionTest(unittest.TestCase):
     with browser_to_create.Create() as b:
       b.Start()
       extension = b.extensions[load_extension]
+      self.assertTrue(
+          extension.EvaluateJavaScript('chrome.runtime != null'))
       extension.ExecuteJavaScript('setTestVar("abcdef")')
       self.assertEquals('abcdef', extension.EvaluateJavaScript('_testVar'))