Reland "ui/aura: Enable the build of demo, bench and unit..."

ui/events/BUILD.gn

Index: ui/events/BUILD.gn
diff --git a/ui/events/BUILD.gn b/ui/events/BUILD.gn
index f93d1eb0b09fb245512f8ab88e5373992b8ae53a..de7fec8c6869828213b2eade60cdb45b697e3b4f 100644
--- a/ui/events/BUILD.gn
+++ b/ui/events/BUILD.gn
@@ -216,6 +216,8 @@ source_set("test_support") {
   sources = [
     "test/cocoa_test_event_utils.h",
     "test/cocoa_test_event_utils.mm",
+    "test/event_generator.cc",
+    "test/event_generator.h",
     "test/events_test_utils.cc",
     "test/events_test_utils.h",
     "test/events_test_utils_x11.cc",
@@ -253,6 +255,14 @@ source_set("test_support") {
       "test/events_test_utils_x11.h",
     ]
   }
+
+  if (is_android) {
+    # Event generator not yet ported to Android.
+    sources -= [
+      "test/event_generator.cc",
+      "test/event_generator.h",
+    ]
+  }
 }
 
 test("events_unittests") {