[DevTools] Add "never show" link to emulation warning.

Source/devtools/front_end/sdk/OverridesSupport.js

Index: Source/devtools/front_end/sdk/OverridesSupport.js
diff --git a/Source/devtools/front_end/sdk/OverridesSupport.js b/Source/devtools/front_end/sdk/OverridesSupport.js
index f649a79f74e3a6ff4c251942072d80efa7d4e00f..6868018e6d2a7ba3c0cf037de34d630797437f5b 100644
--- a/Source/devtools/front_end/sdk/OverridesSupport.js
+++ b/Source/devtools/front_end/sdk/OverridesSupport.js
@@ -474,8 +474,6 @@ WebInspector.OverridesSupport.prototype = {
         WebInspector.settings.showMetricsRulers.addChangeListener(this._showRulersChanged, this);
         this._showRulersChanged();
 
-        WebInspector.settings.disableOverridesWarning.addChangeListener(this._dispatchWarningChanged, this);
-
         if (!this.emulationEnabled())
             return;
 
@@ -761,7 +759,7 @@ WebInspector.OverridesSupport.prototype = {
      */
     warningMessage: function()
     {
-        return WebInspector.settings.disableOverridesWarning.get() ? "" : (this._deviceMetricsWarningMessage || this._userAgentWarningMessage || "");
+        return this._deviceMetricsWarningMessage || this._userAgentWarningMessage || "";
     },
 
     clearWarningMessage: function()