Cleanups for aura/test/event_generator.h (resolve TODOs)

Some purely mechanical changes left over from r283694, now that
aura::test::EventGenerator has moved to ui::test in src/ui/events.

Moves aura/test/event_generator.* to event_generator_delegate_aura.*
Removes `using ui::test::EventGenerator;` declaration and redirects
includes that don't extend the delegate to include the ui/test
event_generator.h directly

BUG=378134

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=285209

Review URL: https://codereview.chromium.org/406413004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285857 0039d316-1c4b-4281-b951-d872f2087c98

diff --git a/ui/aura/BUILD.gn b/ui/aura/BUILD.gn
index c3a69423..6395c560 100644
--- a/ui/aura/BUILD.gn
+++ b/ui/aura/BUILD.gn

@@ -150,8 +150,8 @@
     "test/aura_test_utils.cc",
     "test/aura_test_utils.h",
     "test/env_test_helper.h",
-    "test/event_generator.cc",
-    "test/event_generator.h",
+    "test/event_generator_delegate_aura.cc",
+    "test/event_generator_delegate_aura.h",
     "test/test_cursor_client.cc",
     "test/test_cursor_client.h",
     "test/test_focus_client.cc",