Remove dead code for "colored diff column top borders"

This code was added in 2016 via Iadf7793. The two CSS classes
.mw-revslider-older-diff-column and .mw-revslider-newer-diff-column
became unused only one month later via I317a2fc. Since then all
this is apparently dead code. There are no "top borders" on these
columns any more. Lines still appear in the same position, but as
"border-bottom" on other elements.

It really looks like we just forgot to remove this.

Change-Id: I627628fa44da96ca1f1301d3a879919e4a021e5b

modules/ext.RevisionSlider.DiffPage.js

@@ -75,9 +75,9 @@ $.extend( DiffPage.prototype, {
 
 			self.addHandlersToCoreLinks( sliderView );
 
+			// Re-trigger existing, stable core hooks under the same circumstances as in core
 			mw.hook( 'wikipage.content' ).fire( $contentText );
 			mw.hook( 'wikipage.diff' ).fire( $( document.body ).find( 'table.diff' ) );
-
 		}, function ( xhr ) {
 			$( 'table.diff[data-mw="interface"]' ).removeClass( 'mw-revslider-diff-loading' );
 			if ( xhr.statusText !== 'abort' ) {

modules/ext.RevisionSlider.PointerLine.js

@@ -149,45 +149,12 @@ $.extend( PointerLine.prototype, {
 			);
 	},
 
-	/**
-	 * Adds colored top-borders for the diff columns fitting the line colors between pointers and columns
-	 *
-	 * @param {boolean} [show=true]
-	 * @private
-	 */
-	addColoredColumnBorders: function ( show ) {
-		show = show !== false;
-		$( '#mw-diff-otitle1' ).toggleClass( 'mw-revslider-older-diff-column', show );
-		$( '#mw-diff-ntitle1' ).toggleClass( 'mw-revslider-newer-diff-column', show );
-	},
-
-	/**
-	 * Remove colored top-borders for the diff columns fitting the line colors between pointers and columns
-	 *
-	 * @private
-	 */
-	removeColoredColumnBorders: function () {
-		this.addColoredColumnBorders( false );
-	},
-
-	/**
-	 * Sets the hooks to draw the column borders
-	 *
-	 * @private
-	 */
-	setColumnBorderHooks: function () {
-		mw.hook( 'wikipage.diff' ).add( this.addColoredColumnBorders );
-		mw.hook( 'revslider.expand' ).add( this.addColoredColumnBorders );
-		mw.hook( 'revslider.collapse' ).add( this.removeColoredColumnBorders.bind( this ) );
-	},
-
 	/**
 	 * @return {jQuery}
 	 */
 	getElement: function () {
 		if ( !this.$html ) {
 			this.initialize();
-			this.setColumnBorderHooks();
 		}
 		return this.$html;
 	}

modules/ext.RevisionSlider.init.js

@@ -141,11 +141,9 @@ toggleButton.connect( this, {
 		if ( expanded ) {
 			expand();
 			mw.track( 'counter.MediaWiki.RevisionSlider.event.expand' );
-			mw.hook( 'revslider.expand' ).fire();
 		} else {
 			collapse();
 			mw.track( 'counter.MediaWiki.RevisionSlider.event.collapse' );
-			mw.hook( 'revslider.collapse' ).fire();
 		}
 	}
 } );