Add hooks fired when finished processing compact language links

Bug: T145755
Change-Id: I921191c2cd32d55161b32bad2b2e0d98228cf230

hooks.md

@@ -5,6 +5,13 @@ The hook names are prefixed with mw.uls as a convention.
 
 # List of hooks
 
+## mw.uls.compactlinks.initialized
+
+Fired when the rendering of compact language links and
+the corresponding button is completed.
+Sends a boolean true argument if the list was actually compacted
+and the trigger was rendered, and false otherwise.
+
 ## mw.uls.font.change
 
 Fired when the user changes a webfont.

resources/js/ext.uls.compactlinks.js

@@ -75,6 +75,8 @@
 
 		if ( this.listSize <= max ) {
 			// Not enough languages to compact the list
+			mw.hook( 'mw.uls.compactlinks.initialized' ).fire( false );
+
 			return;
 		}
 
@@ -98,6 +100,8 @@
 		}
 
 		this.addTrigger();
+
+		mw.hook( 'mw.uls.compactlinks.initialized' ).fire( true );
 	};
 
 	/**