DevTools: Move jsdifflib to "sources", extract "toolbox" module

Source/devtools/devtools.gypi

Index: Source/devtools/devtools.gypi
diff --git a/Source/devtools/devtools.gypi b/Source/devtools/devtools.gypi
index 7a086008d58bd659ebb484a258177fe49f59ebf4..a908521c6bfc9f0c0bd266686e214640aa5e916b 100644
--- a/Source/devtools/devtools.gypi
+++ b/Source/devtools/devtools.gypi
@@ -39,6 +39,7 @@
             '<@(devtools_sdk_js_files)',
             '<@(devtools_ui_js_files)',
             '<@(devtools_components_js_files)',
+            '<@(devtools_toolbox_js_files)',
         ],
         'devtools_core_base_files': [
             'front_end/inspector.html',
@@ -46,9 +47,6 @@
             'front_end/InspectorFrontendAPI.js',
             'front_end/InspectorFrontendEventSink.js',
             'front_end/InspectorFrontendHostStub.js',
-            'front_end/jsdifflib.js',
-            'front_end/MediaQueryInspector.js',
-            'front_end/ResponsiveDesignView.js',
             'front_end/ScreencastView.js',
             'front_end/TestController.js',
             'front_end/dialog.css',
@@ -197,7 +195,6 @@
             'front_end/components/HandlerRegistry.js',
             'front_end/components/HelpScreen.js',
             'front_end/components/InspectElementModeController.js',
-            'front_end/components/InspectedPagePlaceholder.js',
             'front_end/components/InspectorView.js',
             'front_end/components/NativeBreakpointsSidebarPane.js',
             'front_end/components/ObjectPopoverHelper.js',
@@ -211,6 +208,11 @@
             'front_end/components/TimelineGrid.js',
             'front_end/components/WorkerFrontendManager.js',
         ],
+        'devtools_toolbox_js_files': [
+            'front_end/toolbox/InspectedPagePlaceholder.js',
+            'front_end/toolbox/MediaQueryInspector.js',
+            'front_end/toolbox/ResponsiveDesignView.js',
+        ],
         'devtools_main_js_files': [
             'front_end/main/AdvancedApp.js',
             'front_end/main/App.js',
@@ -362,6 +364,7 @@
             'front_end/sources/FilteredItemSelectionDialog.js',
             'front_end/sources/InplaceFormatterEditorAction.js',
             'front_end/sources/JavaScriptSourceFrame.js',
+            'front_end/sources/jsdifflib.js',
             'front_end/sources/NavigatorView.js',
             'front_end/sources/Placard.js',
             'front_end/sources/RevisionHistoryView.js',