Android: fixes option to exclude specific annotated Android instrumentation tests.

build/android/pylib/instrumentation/test_jar.py

Index: build/android/pylib/instrumentation/test_jar.py
diff --git a/build/android/pylib/instrumentation/test_jar.py b/build/android/pylib/instrumentation/test_jar.py
index 64dea2c0007b7ebdf94368a56199b7523e6ed54c..e582a1d752d2750480646b2889c1444cb86ded0c 100644
--- a/build/android/pylib/instrumentation/test_jar.py
+++ b/build/android/pylib/instrumentation/test_jar.py
@@ -197,8 +197,9 @@ class TestJar(object):
               '%s has no annotations. Assuming "%s".', test,
               self._DEFAULT_ANNOTATION)
           available_tests.append(test)
-      excluded_tests = self.GetAnnotatedTests(exclude_annotation_list)
-      available_tests = list(set(available_tests) - set(excluded_tests))
+      if exclude_annotation_list:
+        excluded_tests = self.GetAnnotatedTests(exclude_annotation_list)
+        available_tests = list(set(available_tests) - set(excluded_tests))
     else:
       available_tests = [m for m in self.GetTestMethods()
                          if not self.IsPythonDrivenTest(m)]