src/vs/workbench/services/decorations/browser/decorationsService.ts/DecorationRule/_createIconCSSRule
class DecorationRule:	private _createIconCSSRule(icon: ThemeIcon, color: string | undefined, element: HTMLStyleElement, theme: IColorTheme) {

		const index = icon.id.lastIndexOf('~');
		const id = index < 0 ? icon.id : icon.id.substr(0, index);
		const modifier = index < 0 ? '' : icon.id.substr(index + 1);

		const codicon = iconRegistry.get(id);
		if (!codicon || !('fontCharacter' in codicon.definition)) {
			return;
		}
		const charCode = parseInt(codicon.definition.fontCharacter.substr(1), 16);
		createCSSRule(
			`.${this.iconBadgeClassName}::after`,
			`content: "${String.fromCharCode(charCode)}";
			color: ${getColor(theme, color)};
			font-family: codicon;
			font-size: 16px;
			margin-right: 14px;
			font-weight: normal;
			${modifier === 'spin' ? 'animation: codicon-spin 1.5s steps(30) infinite' : ''};
			`,
			element
		);
	}