Move gtk-specific browser main parts stuff to its own file.

chrome/browser/ui/libgtk2ui/chrome_browser_main_extra_parts_views_gtk.h

Index: chrome/browser/ui/libgtk2ui/chrome_browser_main_extra_parts_views_gtk.h
diff --git a/chrome/browser/ui/libgtk2ui/chrome_browser_main_extra_parts_views_gtk.h b/chrome/browser/ui/libgtk2ui/chrome_browser_main_extra_parts_views_gtk.h
new file mode 100644
index 0000000000000000000000000000000000000000..acfacb889696b0d722d315db9efc1166b1b4d74b
--- /dev/null
+++ b/chrome/browser/ui/libgtk2ui/chrome_browser_main_extra_parts_views_gtk.h
@@ -0,0 +1,30 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_UI_LIBGTK2UI_CHROME_BROWSER_MAIN_EXTRA_PARTS_VIEWS_GTK_H_
+#define CHROME_BROWSER_UI_LIBGTK2UI_CHROME_BROWSER_MAIN_EXTRA_PARTS_VIEWS_GTK_H_
+
+#include "base/compiler_specific.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "build/build_config.h"
+#include "chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h"
+
+class ChromeBrowserMainExtraPartsViewsGtk
+    : public ChromeBrowserMainExtraPartsViews {
+ public:
+  ChromeBrowserMainExtraPartsViewsGtk();
+  ~ChromeBrowserMainExtraPartsViewsGtk() override;
+
+  // Overridden from ChromeBrowserMainExtraParts:
+  void PreEarlyInitialization() override;
+  void ToolkitInitialized() override;
+  void PreCreateThreads() override;
+  void PreProfileInit() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ChromeBrowserMainExtraPartsViewsGtk);
+};
+
+#endif  // CHROME_BROWSER_UI_LIBGTK2UI_CHROME_BROWSER_MAIN_EXTRA_PARTS_VIEWS_GTK_H_