Expose AppUi from devil utils in browser

telemetry/telemetry/internal/backends/chrome/android_browser_backend.py

Index: telemetry/telemetry/internal/backends/chrome/android_browser_backend.py
diff --git a/telemetry/telemetry/internal/backends/chrome/android_browser_backend.py b/telemetry/telemetry/internal/backends/chrome/android_browser_backend.py
index 763f9655f51de9e1e7a7381d9c2e20eaa4c6b96e..681921947ea8019a5b7c38a67e969ae2de53d223 100644
--- a/telemetry/telemetry/internal/backends/chrome/android_browser_backend.py
+++ b/telemetry/telemetry/internal/backends/chrome/android_browser_backend.py
@@ -67,6 +67,14 @@ class AndroidBrowserBackend(chrome_browser_backend.ChromeBrowserBackend):
   def device(self):
     return self.platform_backend.device
 
+  @property
+  def supports_app_ui_interactions(self):
+    return True
+
+  @property
+  def app_ui(self):
+    return app_ui.AppUi(self.device, package=self.package)

[perezju, 2017/04/05 08:46:44]

Can you cache the value after its first use as in:
https://github.com/catapult-project/catapult/blob/master/telemetry/telemetry/...

Also make it a regular method (not property) here. 

[ssid, 2017/04/13 20:07:39]

Done.

+
   def _StopBrowser(self):
     # Note: it's important to stop and _not_ kill the browser app, since
     # stopping also clears the app state in Android's activity manager.