Change the visual appearance of panel on GTK per new UI design.

chrome/chrome_browser.gypi

Index: chrome/chrome_browser.gypi
diff --git a/chrome/chrome_browser.gypi b/chrome/chrome_browser.gypi
index 631e83733fe9d518e80821879e55614bd1a7ea9d..2a0e5fadf071dbd820bfffd67546e983c854e3cc 100644
--- a/chrome/chrome_browser.gypi
+++ b/chrome/chrome_browser.gypi
@@ -2885,6 +2885,7 @@
         'browser/ui/gtk/browser_actions_toolbar_gtk.h',
         'browser/ui/gtk/browser_titlebar.cc',
         'browser/ui/gtk/browser_titlebar.h',
+        'browser/ui/gtk/browser_titlebar_base.h',
         'browser/ui/gtk/browser_toolbar_gtk.cc',
         'browser/ui/gtk/browser_toolbar_gtk.h',
         'browser/ui/gtk/browser_window_gtk.cc',
@@ -3085,6 +3086,8 @@
         'browser/ui/gtk/task_manager_gtk.h',
         'browser/ui/gtk/throbber_gtk.cc',
         'browser/ui/gtk/throbber_gtk.h',
+        'browser/ui/gtk/titlebar_throb_animation.cc',
+        'browser/ui/gtk/titlebar_throb_animation.h',
         'browser/ui/gtk/unity_service.cc',
         'browser/ui/gtk/unity_service.h',
         'browser/ui/gtk/update_recommended_dialog.cc',
@@ -3148,10 +3151,10 @@
         'browser/ui/panels/panel_bounds_animation.h',
         'browser/ui/panels/panel_browser_frame_view.cc',
         'browser/ui/panels/panel_browser_frame_view.h',
-        'browser/ui/panels/panel_browser_view.cc',
-        'browser/ui/panels/panel_browser_view.h',
         'browser/ui/panels/panel_browser_titlebar_gtk.cc',
         'browser/ui/panels/panel_browser_titlebar_gtk.h',
+        'browser/ui/panels/panel_browser_view.cc',
+        'browser/ui/panels/panel_browser_view.h',
         'browser/ui/panels/panel_browser_window.cc',
         'browser/ui/panels/panel_browser_window.h',
         'browser/ui/panels/panel_browser_window_cocoa.h',