Moving some functions from browser to app. Adding function prototypes to app backend.

tools/telemetry/telemetry/core/backends/browser_backend.py

Index: tools/telemetry/telemetry/core/backends/browser_backend.py
diff --git a/tools/telemetry/telemetry/core/backends/browser_backend.py b/tools/telemetry/telemetry/core/backends/browser_backend.py
index 44f96c0c36af0a0e270a4367d18196ba9c685403..e56a3d26d25755bd015d8a99977b4ce3c042f94e 100644
--- a/tools/telemetry/telemetry/core/backends/browser_backend.py
+++ b/tools/telemetry/telemetry/core/backends/browser_backend.py
@@ -20,17 +20,15 @@ class BrowserBackend(app_backend.AppBackend):
 
   def __init__(self, supports_extensions, browser_options, tab_list_backend):
     assert browser_options.browser_type
-    super(BrowserBackend, self).__init__()
-    self.browser_type = browser_options.browser_type
+    super(BrowserBackend, self).__init__(app_type=browser_options.browser_type)
     self._supports_extensions = supports_extensions
     self.browser_options = browser_options
-    self._browser = None
     self._tab_list_backend_class = tab_list_backend
     self._forwarder_factory = None
     self._wpr_ca_cert_path = None
 
   def SetBrowser(self, browser):
-    self._browser = browser
+    super(BrowserBackend, self).SetApp(app=browser)
     if self.browser_options.netsim:
       host_platform = platform.GetHostPlatform()
       if not host_platform.CanLaunchApplication('ipfw'):
@@ -38,7 +36,11 @@ class BrowserBackend(app_backend.AppBackend):
 
   @property
   def browser(self):
-    return self._browser
+    return self.app
+
+  @property
+  def browser_type(self):
+    return self.app_type
 
   @property
   def supports_extensions(self):
@@ -106,6 +108,9 @@ class BrowserBackend(app_backend.AppBackend):
   def IsBrowserRunning(self):
     raise NotImplementedError()
 
+  def IsAppRunning(self):
+    return self.IsBrowserRunning()
+
   def GetStandardOutput(self):
     raise NotImplementedError()