lib/Ext/core/class/Base.js
function(name, mixinClass) {
            var mixin = mixinClass.prototype,
                prototype = this.prototype,
                key;

            if (typeof mixin.onClassMixedIn != 'undefined') {
                mixin.onClassMixedIn.call(mixinClass, this);
            }

            if (!prototype.hasOwnProperty('mixins')) {
                if ('mixins' in prototype) {
                    prototype.mixins = Ext.Object.chain(prototype.mixins);
                }
                else {
                    prototype.mixins = {};
                }
            }

            for (key in mixin) {
                if (key === 'mixins') {
                    Ext.merge(prototype.mixins, mixin[key]);
                }
                else if (typeof prototype[key] == 'undefined' && key != 'mixinId' && key != 'config') {
                    prototype[key] = mixin[key];
                }
            }

            //<feature classSystem.config>
            if ('config' in mixin) {
                this.addConfig(mixin.config, false);
            }
            //</feature>

            prototype.mixins[name] = mixin;
        }
function(name, mixinClass) {
            var mixin = mixinClass.prototype,
                prototype = this.prototype,
                key;

            if (typeof mixin.onClassMixedIn != 'undefined') {
                mixin.onClassMixedIn.call(mixinClass, this);
            }

            if (!prototype.hasOwnProperty('mixins')) {
                if ('mixins' in prototype) {
                    prototype.mixins = Ext.Object.chain(prototype.mixins);
                }
                else {
                    prototype.mixins = {};
                }
            }

            for (key in mixin) {
                if (key === 'mixins') {
                    Ext.merge(prototype.mixins, mixin[key]);
                }
                else if (typeof prototype[key] == 'undefined' && key != 'mixinId' && key != 'config') {
                    prototype[key] = mixin[key];
                }
            }

            //<feature classSystem.config>
            if ('config' in mixin) {
                this.addConfig(mixin.config, false);
            }
            //</feature>

            prototype.mixins[name] = mixin;
        }
<feature classSystem.mixins> 
Used internally by the mixins pre-processor
@private
@static
@inheritable