[android] Adds constants.GetOutDirectory() and converts test scripts to use it.

build/android/pylib/host_driven/test_case.py

Index: build/android/pylib/host_driven/test_case.py
diff --git a/build/android/pylib/host_driven/test_case.py b/build/android/pylib/host_driven/test_case.py
index 3387c948bdda3bb30a0686204faefb3f64b8e526..3c677939f414782a2570f639c9a6362e1a510902 100644
--- a/build/android/pylib/host_driven/test_case.py
+++ b/build/android/pylib/host_driven/test_case.py
@@ -68,9 +68,10 @@ class HostDrivenTestCase(object):
   def TearDown(self):
     pass
 
+  # TODO(craigdh): Remove GetOutDir once references have been removed
+  # downstream.
   def GetOutDir(self):
-    return os.path.join(os.environ['CHROME_SRC'], 'out',
-                        constants.GetBuildType())
+    return constants.GetOutDirectory()
 
   def Run(self):
     logging.info('Running host-driven test: %s', self.tagged_name)