DevTools: remove the ComputedStyles -> Styles pane dependency.

third_party/WebKit/Source/devtools/front_end/elements/StylesSidebarPane.js

Index: third_party/WebKit/Source/devtools/front_end/elements/StylesSidebarPane.js
diff --git a/third_party/WebKit/Source/devtools/front_end/elements/StylesSidebarPane.js b/third_party/WebKit/Source/devtools/front_end/elements/StylesSidebarPane.js
index 8530344b19d9b7fd7017cad92a817dfce8816eef..3b98d610b1543273d8009404c7bcf5078ba26e5f 100644
--- a/third_party/WebKit/Source/devtools/front_end/elements/StylesSidebarPane.js
+++ b/third_party/WebKit/Source/devtools/front_end/elements/StylesSidebarPane.js
@@ -242,26 +242,26 @@ WebInspector.StylesSidebarPane.prototype = {
     {
         this._discardElementUnderMouse();
 
-        return this.fetchMatchedCascade()
+        return this._fetchMatchedCascade()
             .then(this._innerRebuildUpdate.bind(this));
     },
 
     _resetCache: function()
     {
-        delete this._matchedCascadePromise;
+        if (this.cssModel())
+            this.cssModel().discardCachedMatchedCascade();
     },
 
     /**
      * @return {!Promise.<?WebInspector.CSSMatchedStyles>}
      */
-    fetchMatchedCascade: function()
+    _fetchMatchedCascade: function()
     {
         var node = this.node();
-        if (!node)
+        if (!node || !this.cssModel())
             return Promise.resolve(/** @type {?WebInspector.CSSMatchedStyles} */(null));
-        if (!this._matchedCascadePromise)
-            this._matchedCascadePromise = this._matchedStylesForNode(node).then(validateStyles.bind(this));
-        return this._matchedCascadePromise;
+
+        return this.cssModel().cachedMatchedCascadeForNode(node).then(validateStyles.bind(this));
 
         /**
          * @param {?WebInspector.CSSMatchedStyles} matchedStyles
@@ -275,18 +275,6 @@ WebInspector.StylesSidebarPane.prototype = {
     },
 
     /**
-     * @param {!WebInspector.DOMNode} node
-     * @return {!Promise.<?WebInspector.CSSMatchedStyles>}
-     */
-    _matchedStylesForNode: function(node)
-    {
-        var cssModel = this.cssModel();
-        if (!cssModel)
-            return Promise.resolve(/** @type {?WebInspector.CSSMatchedStyles} */(null));
-        return cssModel.matchedStylesPromise(node.id)
-    },
-
-    /**
      * @param {boolean} editing
      */
     setEditingStyle: function(editing)