[test] Refactoring - Use subject/observer pattern for progress indicators.

tools/run-tests.py

Index: tools/run-tests.py
diff --git a/tools/run-tests.py b/tools/run-tests.py
index 78a7edc35e9614f291a43bc1a35ed5dd50551a29..7fa7414963064c440c4d0f29b623d072d8725af1 100755
--- a/tools/run-tests.py
+++ b/tools/run-tests.py
@@ -614,14 +614,14 @@ def Execute(arch, mode, args, options, suites, workspace):
 
   # Run the tests, either locally or distributed on the network.
   start_time = time.time()
-  progress_indicator = progress.PROGRESS_INDICATORS[options.progress]()
+  progress_indicator = progress.IndicatorNotifier()
+  progress_indicator.Register(progress.PROGRESS_INDICATORS[options.progress]())
   if options.junitout:
-    progress_indicator = progress.JUnitTestProgressIndicator(
-        progress_indicator, options.junitout, options.junittestsuite)
+    progress_indicator.Register(progress.JUnitTestProgressIndicator(
+        options.junitout, options.junittestsuite))
   if options.json_test_results:
-    progress_indicator = progress.JsonTestProgressIndicator(
-        progress_indicator, options.json_test_results, arch,
-        MODES[mode]["execution_mode"])
+    progress_indicator.Register(progress.JsonTestProgressIndicator(
+        options.json_test_results, arch, MODES[mode]["execution_mode"]))
 
   run_networked = not options.no_network
   if not run_networked: