[Android] Rewrite base test result classes.

build/android/pylib/instrumentation/test_package.py

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Class representing instrumentation test apk and jar."""
 
 import os
 
 from pylib.utils import apk_helper
 
 import test_jar
 
 
 class TestPackage(test_jar.TestJar):
   def __init__(self, apk_path, jar_path):
     test_jar.TestJar.__init__(self, jar_path)
 
     if not os.path.exists(apk_path):
       raise Exception('%s not found, please build it' % apk_path)
     self._apk_path = apk_path
+    self._package_name = apk_helper.GetPackageName(self._apk_path)
 
   def GetApkPath(self):
     return self._apk_path
 
   def GetPackageName(self):
     """Returns the package name of this APK."""
-    return apk_helper.GetPackageName(self._apk_path)
+    return self._package_name
 
   # Override.
   def Install(self, adb):
     adb.ManagedInstall(self.GetApkPath(), package_name=self.GetPackageName())