Call onProgress, onError of duplicate requests in FileLoader

[ngokevin]

Description of the problem

Duplicate request handling in #12434

In case of an error on the request, we should notify the rest of the duplicate .load() callbacks (onError). Similarly, we can call onProgress to every duplicate .load() call callback.

Three.js version

• Dev
• r87
• ...

Browser

• All of them
• Chrome
• Firefox
• Internet Explorer

OS

• All of them
• Windows
• macOS
• Linux
• Android
• iOS

Hardware Requirements (graphics card, VR Device, ...)

[takahirox]

I've found another issue.

When Cache.enabled is false, duplicate requests aren't handled correctly because cached is always undefined here

three.js/src/loaders/FileLoader.js

Line 28 in 613499d

if ( cached !== undefined ) {

and loading[ url ] isn't deleted when callback function is called.

three.js/src/loaders/FileLoader.js

Lines 193 to 199 in 613499d

	for ( var i = 0; i < callbacks.length; i ++ ) {
	callbacks[ i ]( response );
	}
	delete loading[ url ];

then calllback function is registered again here.

three.js/src/loaders/FileLoader.js

Lines 46 to 56 in 613499d

	if ( loading[ url ] !== undefined ) {
	loading[ url ].push( function () {
	scope.load( url, onLoad, onProgress, onError );
	} );
	return;
	}

I'm trying to fix all...

/cc @mrdoob