Fix coverage to work in IE8

IE8 has a bit differrent CCSOM structure

lib/browser/client-scripts/gemini.coverage.js

@@ -8,28 +8,29 @@
             sheets = document.styleSheets;
         try {
             for (var i = 0; i < sheets.length; i++) {
-                var rules = sheets[i].cssRules,
+                var rules = sheets[i].cssRules || sheets[i].rules,
                     ctx = {
                         // media rule counter
                         // coverage for media rules is stored by its index within stylesheet
                         media: -1,
+                        href: sheets[i].href,
                         coverage: coverage
                     };
                 for (var r = 0; r < rules.length; r++) {
-                    coverageRule(rules[r], rect, ctx);
+                    coverageForRule(rules[r], rect, ctx);
                 }
             }
         } catch (e) {
             return {
                 error: 'JS',
-                message: e.stack
+                message: e.stack || e.message
             };
         }
 
         return coverage;
     };
 
-    function coverageRule(rule, area, ctx) {
+    function coverageForRule(rule, area, ctx) {
         if (rule.cssRules || rule.styleSheet) {
             if (rule.conditionText) {
                 ctx.media++;
@@ -40,7 +41,7 @@
 
             var rules = rule.cssRules || rule.styleSheet.cssRules;
             for (var r = 0; r < rules.length; r++) {
-                coverageRule(rules[r], area, ctx);
+                coverageForRule(rules[r], area, ctx);
             }
 
             return;
@@ -77,7 +78,7 @@
                 }
             }
 
-            var byfile = ctx.coverage[rule.parentStyleSheet.href] = ctx.coverage[rule.parentStyleSheet.href] || {};
+            var byfile = ctx.coverage[ctx.href] = ctx.coverage[ctx.href] || {};
             if (rule.parentRule && rule.parentRule.conditionText) {
                 selector = '?' + ctx.media + ':' + selector;
             }