Devtools: Introduce WI.ExtensibleToolbar

Source/devtools/front_end/main/module.json

Index: Source/devtools/front_end/main/module.json
diff --git a/Source/devtools/front_end/main/module.json b/Source/devtools/front_end/main/module.json
index 192338604a8f349f0d1d58ea80dbf1368bce0e33..928df4f1ef2a79bf23200ada1b736f9aafa87710 100644
--- a/Source/devtools/front_end/main/module.json
+++ b/Source/devtools/front_end/main/module.json
@@ -168,7 +168,7 @@
         {
             "type": "@WebInspector.ToolbarItem.Provider",
             "className": "WebInspector.InspectElementModeController.ToggleButtonProvider",
-            "location": "toolbar-left",
+            "location": "main-toolbar-left",
             "order": 0,
             "actionId": "main.toggle-element-search"
         },
@@ -177,25 +177,25 @@
             "className": "WebInspector.AdvancedApp.EmulationButtonProvider",
             "condition": "can_dock",
             "order": 1,
-            "location": "toolbar-left"
+            "location": "main-toolbar-left"
         },
         {
             "type": "@WebInspector.ToolbarItem.Provider",
             "className": "WebInspector.Main.WarningErrorCounter",
             "order": 1,
-            "location": "toolbar-right"
+            "location": "main-toolbar-right"
         },
         {
             "type": "@WebInspector.ToolbarItem.Provider",
             "className": "WebInspector.InspectorView.ToggleDrawerButtonProvider",
             "order": 2,
-            "location": "toolbar-right"
+            "location": "main-toolbar-right"
         },
         {
             "type": "@WebInspector.ToolbarItem.Provider",
             "className": "WebInspector.DockController.ButtonProvider",
             "order": 4,
-            "location": "toolbar-right"
+            "location": "main-toolbar-right"
         },
         {
             "type": "setting",