Update AppRTCDemo resolution for iPhone6/6+

BUG=

Review URL: https://codereview.webrtc.org/1214113015

Cr-Commit-Position: refs/heads/master@{#9530}
diff --git a/talk/libjingle_examples.gyp b/talk/libjingle_examples.gyp
index 8a08481..5cd31b6 100755
--- a/talk/libjingle_examples.gyp
+++ b/talk/libjingle_examples.gyp
@@ -222,7 +222,9 @@
           'conditions': [
             ['OS=="ios"', {
               'mac_bundle_resources': [
-                'examples/objc/AppRTCDemo/ios/resources/Default-568h.png',
+                'examples/objc/AppRTCDemo/ios/resources/iPhone5@2x.png',
+                'examples/objc/AppRTCDemo/ios/resources/iPhone6@2x.png',
+                'examples/objc/AppRTCDemo/ios/resources/iPhone6p@3x.png',
                 'examples/objc/AppRTCDemo/ios/resources/Roboto-Regular.ttf',
                 'examples/objc/AppRTCDemo/ios/resources/ic_call_end_black_24dp.png',
                 'examples/objc/AppRTCDemo/ios/resources/ic_call_end_black_24dp@2x.png',