MDL-50795 atto: Pasting into atto removes background colour style.

Copying from one atto editor to another comes with a lot of style
information. This removes the color attributes which make the page
look ugly when competing with different themes.

lib/editor/atto/yui/build/moodle-editor_atto-editor/moodle-editor_atto-editor-debug.js

@@ -1314,6 +1314,8 @@ EditorClean.prototype = {
             {regex: /(<[^>]*?style\s*?=\s*?")([^>"]*)(")/gi, replace: function(match, group1, group2, group3) {
                     // Remove MSO-blah, MSO:blah style attributes.
                     group2 = group2.replace(/(?:^|;)[\s]*MSO[-:](?:&[\w]*;|[^;"])*/gi,"");
+                    // Remove backgroud color style.
+                    group2 = group2.replace(/background-color:.*?;/gi,"");
                     return group1 + group2 + group3;
                 }},
             // Get all class attributes so we can work on them.

lib/editor/atto/yui/build/moodle-editor_atto-editor/moodle-editor_atto-editor.js

@@ -1303,6 +1303,8 @@ EditorClean.prototype = {
             {regex: /(<[^>]*?style\s*?=\s*?")([^>"]*)(")/gi, replace: function(match, group1, group2, group3) {
                     // Remove MSO-blah, MSO:blah style attributes.
                     group2 = group2.replace(/(?:^|;)[\s]*MSO[-:](?:&[\w]*;|[^;"])*/gi,"");
+                    // Remove backgroud color style.
+                    group2 = group2.replace(/background-color:.*?;/gi,"");
                     return group1 + group2 + group3;
                 }},
             // Get all class attributes so we can work on them.

lib/editor/atto/yui/src/editor/js/clean.js

@@ -290,6 +290,8 @@ EditorClean.prototype = {
             {regex: /(<[^>]*?style\s*?=\s*?")([^>"]*)(")/gi, replace: function(match, group1, group2, group3) {
                     // Remove MSO-blah, MSO:blah style attributes.
                     group2 = group2.replace(/(?:^|;)[\s]*MSO[-:](?:&[\w]*;|[^;"])*/gi,"");
+                    // Remove backgroud color style.
+                    group2 = group2.replace(/background-color:.*?;/gi,"");
                     return group1 + group2 + group3;
                 }},
             // Get all class attributes so we can work on them.