Cherry pick 18.4 changes to udc-widevine-dev

Get the udc-widevine-dev Android branch and oemcrypto-v18 cdm branch in
sync. The commit ID for 18.4 on oemcrypto-v18 is
a2f23a2281e5e06dc2867585bdc516fa132b6396.

Merged from go/wvgerrit/190151

Bug: 290252845
Test: WVTS tests are running and passing
Change-Id: I457332e7ca70a5b5169345e1279b3eb9f18413b6

libwvdrmengine/cdm/test/dummy_app.mm

@@ -0,0 +1,14 @@
+// Copyright 2019 Google LLC. All Rights Reserved.
+
+#import <UIKit/UIKit.h>
+
+@interface AppDelegate : UIResponder <UIApplicationDelegate>
+@end
+
+@implementation AppDelegate {
+}
+@end
+
+int main(int argc, char** argv) {
+  return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
+}