MDL-64375 gradingform_rubric: Styles for overflow

Allow people to define lots of levels, and make the scroll region just the rubric table,
not the entire content region.

grade/grading/form/rubric/styles.css

@@ -64,10 +64,7 @@
 }
 
 .gradingform_rubric {
-    overflow: auto;
     padding-bottom: 1.5em;
-    max-width: 720px;
-    position: relative;
 }
 
 .gradingform_rubric.editor .criterion .controls,
@@ -89,6 +86,9 @@
 
 .gradingform_rubric .criteria {
     height: 100%;
+    display: flex;
+    width: 100%;
+    overflow: auto;
 }
 
 .gradingform_rubric .criterion {
@@ -307,4 +307,4 @@
     margin: 0;
     position: relative;
     float: right;
-}
+}

mod/assign/styles.css

@@ -760,8 +760,11 @@
 /***** Start rubric *****/
 
 .path-mod-assign [data-region="grade-panel"] .gradingform_rubric {
+    max-width: 100%;
     padding-bottom: 0;
-    max-width: none;
+}
+.path-mod-assign .gradingform_rubric {
+    max-width: calc(100vw - 200px);
 }
 
 .path-mod-assign [data-region="grade-panel"] .gradingform_rubric .criterion .description {