Added the --screenshot option.

build/android/pylib/instrumentation/instrumentation_test_instance.py

Index: build/android/pylib/instrumentation/instrumentation_test_instance.py
diff --git a/build/android/pylib/instrumentation/instrumentation_test_instance.py b/build/android/pylib/instrumentation/instrumentation_test_instance.py
index 610f084ba054b787488f49cc00ef860143db3396..a87cb8626ce5a1e86dbdb6f5a16d229037334f0c 100644
--- a/build/android/pylib/instrumentation/instrumentation_test_instance.py
+++ b/build/android/pylib/instrumentation/instrumentation_test_instance.py
@@ -386,6 +386,7 @@ class InstrumentationTestInstance(test_instance.TestInstance):
       self._driver_apk = None
 
   def _initializeTestControlAttributes(self, args):
+    self._screenshot_dir = args.screenshot_dir
     self._timeout_scale = args.timeout_scale or 1
 
   @property
@@ -421,6 +422,10 @@ class InstrumentationTestInstance(test_instance.TestInstance):
     return self._package_info
 
   @property
+  def screenshot_dir(self):
+    return self._screenshot_dir
+
+  @property
   def suite(self):
     return self._suite