avm2: Correctly apply 'skip_next_enter_frame' to Loader

We were missing the initial 'set_skip_next_enter_frame(true)'
call, and we weren't properly clearing it in `enter_frame`.
Loaders appear to have the same behavior as MovieClips.

This makes us correctly run the first framescript for the loaded
SWF.

core/src/display_object/loader_display.rs

@@ -117,6 +117,8 @@ impl<'gc> TDisplayObject<'gc> for LoaderDisplay<'gc> {
             }
             child.enter_frame(context);
         }
+        self.base_mut(context.gc_context)
+            .set_skip_next_enter_frame(false);
     }
 
     fn construct_frame(&self, context: &mut UpdateContext<'_, 'gc>) {

core/src/loader.rs

@@ -640,6 +640,12 @@ impl<'gc> Loader<'gc> {
             // 'this.parent == null' and 'this.stage == null'
             mc.post_instantiation(context, None, Instantiator::Movie, false);
             catchup_display_object_to_frame(context, mc.into());
+            // Movie clips created from ActionScript (including from a Loader) skip the next enterFrame,
+            // and consequently are observed to have their currentFrame lag one
+            // frame behind objects placed by the timeline (even if they were
+            // both placed in the same frame to begin with).
+            mc.base_mut(context.gc_context)
+                .set_skip_next_enter_frame(true);
 
             if let Some(MovieLoaderEventHandler::Avm2LoaderInfo(loader_info)) = event_handler {
                 let mut activation = Avm2Activation::from_nothing(context.reborrow());

tests/tests/swfs/avm2/loader_loadbytes_events/output.txt

@@ -4,10 +4,14 @@ loader.contentLoaderInfo.bytesLoaded = 0
 loader.contentLoaderInfo.bytesTotal = 0
 loader.contentLoaderInfo.bytes = null
 loader.contentLoaderInfo.url = null
-Event [ProgressEvent type="progress" bubbles=false cancelable=false eventPhase=2 bytesLoaded=0 bytesTotal=674]: loader.numChildren = 0, loader.content = null, loader.contentLoaderInfo.bytesLoaded = 0, loader.contentLoaderInfo.bytesTotal = 674, loader.contentLoaderInfo.url = null
+Event [ProgressEvent type="progress" bubbles=false cancelable=false eventPhase=2 bytesLoaded=0 bytesTotal=738]: loader.numChildren = 0, loader.content = null, loader.contentLoaderInfo.bytesLoaded = 0, loader.contentLoaderInfo.bytesTotal = 738, loader.contentLoaderInfo.url = null
-Event [ProgressEvent type="progress" bubbles=false cancelable=false eventPhase=2 bytesLoaded=674 bytesTotal=674]: loader.numChildren = 0, loader.content = null, loader.contentLoaderInfo.bytesLoaded = 674, loader.contentLoaderInfo.bytesTotal = 674, loader.contentLoaderInfo.url = null
+Event [ProgressEvent type="progress" bubbles=false cancelable=false eventPhase=2 bytesLoaded=738 bytesTotal=738]: loader.numChildren = 0, loader.content = null, loader.contentLoaderInfo.bytesLoaded = 738, loader.contentLoaderInfo.bytesTotal = 738, loader.contentLoaderInfo.url = null
+Framescript frame 1
 Hello from loaded SWF!
 loader.contentLoaderInfo === loader.content.loaderInfo : true
 loader.contentLoaderInfo.content === loader.content : true
-Event [Event type="init" bubbles=false cancelable=false eventPhase=2]: loader.numChildren = 1, loader.content = [object LoadableMainTimeline], loader.contentLoaderInfo.bytesLoaded = 674, loader.contentLoaderInfo.bytesTotal = 674, loader.contentLoaderInfo.url = file:///
+Event [Event type="init" bubbles=false cancelable=false eventPhase=2]: loader.numChildren = 1, loader.content = [object LoadableMainTimeline], loader.contentLoaderInfo.bytesLoaded = 738, loader.contentLoaderInfo.bytesTotal = 738, loader.contentLoaderInfo.url = file:///
-Event [Event type="complete" bubbles=false cancelable=false eventPhase=2]: loader.numChildren = 1, loader.content = [object LoadableMainTimeline], loader.contentLoaderInfo.bytesLoaded = 674, loader.contentLoaderInfo.bytesTotal = 674, loader.contentLoaderInfo.url = file:///
+Event [Event type="complete" bubbles=false cancelable=false eventPhase=2]: loader.numChildren = 1, loader.content = [object LoadableMainTimeline], loader.contentLoaderInfo.bytesLoaded = 738, loader.contentLoaderInfo.bytesTotal = 738, loader.contentLoaderInfo.url = file:///
+Framescript frame 2
+Framescript frame 1
+Hello from loaded SWF!

tests/tests/swfs/avm2/loader_loadbytes_events/test.toml

@@ -1,4 +1,4 @@
-num_frames = 3
+num_frames = 4
 
 [image_comparison]
 tolerance = 0