DevTools: Implement extension-based status bar buttons

Source/devtools/front_end/main/module.json

 {
     "extensions": [
         {
             "type": "@WebInspector.ActionDelegate",
             "actionId": "main.reload",
             "className": "WebInspector.Main.ReloadActionDelegate",
             "bindings": [
                 {
                     "platform": "windows,linux",
                     "shortcut": "F5 Ctrl+R"
@@ skipping 93 matching lines @@
                     "platform": "windows,linux",
                     "shortcut": "Ctrl+0 Ctrl+Numpad0"
                 },
                 {
                     "platform": "mac",
                     "shortcut": "Meta+0 Meta+Numpad0"
                 }
             ]
         },
         {
+            "type": "@WebInspector.StatusBarButton.Provider",
+            "className": "WebInspector.AdvancedApp.ResponsiveDesignButtonProvider",
+            "location": "toolbar-left"
+        },
+        {
             "type": "ui-setting",
             "title": "Disable cache (while DevTools is open)",
             "settingName": "cacheDisabled",
             "settingType": "checkbox"
         },
         {
             "type": "ui-setting",
             "section": "Appearance",
             "title": "Split panels vertically when docked to right",
             "settingName": "splitVerticallyWhenDockedToRight",
             "settingType": "checkbox"
         },
         {
             "type": "ui-setting",
             "section": "Appearance",
             "settingType": "custom",
             "className": "WebInspector.Main.ShortcutPanelSwitchSettingDelegate"
         },
         {
             "type": "ui-setting",
             "section": "Extensions",
             "settingType": "custom",
             "className": "WebInspector.HandlerRegistry.OpenAnchorLocationSettingDelegate"
         }
     ]
 }