DevTools: use target-based model accessors only.

Source/devtools/front_end/sdk/CSSStyleModel.js

Index: Source/devtools/front_end/sdk/CSSStyleModel.js
diff --git a/Source/devtools/front_end/sdk/CSSStyleModel.js b/Source/devtools/front_end/sdk/CSSStyleModel.js
index bcf82456e5153bc7baf40377e02c8e001ed263e0..a393e0eb5ca71c0c8eb807fefdac44fa14170cf1 100644
--- a/Source/devtools/front_end/sdk/CSSStyleModel.js
+++ b/Source/devtools/front_end/sdk/CSSStyleModel.js
@@ -692,15 +692,16 @@ WebInspector.CSSStyleDeclaration = function(cssModel, payload)
 }
 
 /**
+ * @param {!WebInspector.Target} target
  * @return {!WebInspector.CSSStyleDeclaration}
  */
-WebInspector.CSSStyleDeclaration.createDummyStyle = function()
+WebInspector.CSSStyleDeclaration.createDummyStyle = function(target)
 {
     var dummyPayload = {
         shorthandEntries: [],
         cssProperties: []
     };
-    return new WebInspector.CSSStyleDeclaration(WebInspector.cssModel, dummyPayload);
+    return new WebInspector.CSSStyleDeclaration(target.cssModel, dummyPayload);
 }
 
 /**
@@ -1818,8 +1819,3 @@ WebInspector.CSSStyleModel.ComputedStyleLoader.prototype = {
         }
     }
 }
-
-/**
- * @type {!WebInspector.CSSStyleModel}
- */
-WebInspector.cssModel;