Dispatch view.event_added over the added half of the changed range

fb75510 pointed it at the removed half, so it fired on departing downloads instead.

test/core/test_view.h

@@ -0,0 +1,15 @@
+#include "test/helpers/test_main_thread.h"
+
+class TestView : public TestFixtureWithMainThread {
+  CPPUNIT_TEST_SUITE(TestView);
+
+  CPPUNIT_TEST(test_filter_dispatches_events_to_the_right_downloads);
+
+  CPPUNIT_TEST_SUITE_END();
+
+public:
+  void setUp();
+  void tearDown();
+
+  void test_filter_dispatches_events_to_the_right_downloads();
+};