Bug 1415940 Part 7: Change canSetRuleText() to test the sheet for modification by CSSOM. r=tromey

MozReview-Commit-ID: 2tCVgntiRHn

--HG--
extra : rebase_source : 99d17cfd55dd0819d8e7a8395a29fb854cd03e3b

devtools/server/actors/styles.js

@@ -1002,10 +1002,10 @@ var StyleRuleActor = protocol.ActorClassWithSpec(styleRuleSpec, {
   get canSetRuleText() {
     return this.type === ELEMENT_STYLE ||
            (this._parentSheet &&
-            // If a rule does not have source, then it has been modified via
-            // CSSOM; and we should fall back to non-authored editing.
+            // If a rule has been modified via CSSOM, then we should fall
+            // back to non-authored editing.
             // https://bugzilla.mozilla.org/show_bug.cgi?id=1224121
-            this.sheetActor.allRulesHaveSource() &&
+            !this.sheetActor.hasRulesModifiedByCSSOM() &&
             // Special case about:PreferenceStyleSheet, as it is generated on
             // the fly and the URI is not registered with the about:handler
             // https://bugzilla.mozilla.org/show_bug.cgi?id=935803#c37

devtools/server/actors/stylesheets.js

@@ -237,27 +237,11 @@ var StyleSheetActor = protocol.ActorClassWithSpec(styleSheetSpec, {
   },
 
   /**
-   * Test whether all the rules in this sheet have associated source.
-   * @return {Boolean} true if all the rules have source; false if
-   *         some rule was created via CSSOM.
+   * Test whether this sheet has been modified by CSSOM.
+   * @return {Boolean} true if changed by CSSOM.
    */
-  allRulesHaveSource: function () {
-    let rules;
-    try {
-      rules = this.rawSheet.cssRules;
-    } catch (e) {
-      // sheet isn't loaded yet
-      return true;
-    }
-
-    for (let i = 0; i < rules.length; i++) {
-      let rule = rules[i];
-      if (InspectorUtils.getRelativeRuleLine(rule) === 0) {
-        return false;
-      }
-    }
-
-    return true;
+  hasRulesModifiedByCSSOM: function () {
+    return InspectorUtils.hasRulesModifiedByCSSOM(this.rawSheet);
   },
 
   /**