Add key modifier to minimize/restore button click to minimize/restore-all panels for GTK

chrome/browser/ui/panels/panel_browser_titlebar_gtk.h

Index: chrome/browser/ui/panels/panel_browser_titlebar_gtk.h
diff --git a/chrome/browser/ui/panels/panel_browser_titlebar_gtk.h b/chrome/browser/ui/panels/panel_browser_titlebar_gtk.h
index fe5772f65d1121879b1410c4b6dcb885bbf5c0f6..9837ebe733a92365e15f554d057d7d837f116163 100644
--- a/chrome/browser/ui/panels/panel_browser_titlebar_gtk.h
+++ b/chrome/browser/ui/panels/panel_browser_titlebar_gtk.h
@@ -15,6 +15,9 @@ class PanelBrowserTitlebarGtk : public BrowserTitlebar {
                           GtkWindow* window);
   virtual ~PanelBrowserTitlebarGtk();
 
+  // Overridden from BrowserTitlebar:
+  virtual void Init() OVERRIDE;
+
   void UpdateMinimizeRestoreButtonVisibility();
 
  protected:
@@ -38,6 +41,11 @@ class PanelBrowserTitlebarGtk : public BrowserTitlebar {
     return unminimize_button_.get();
   }
 
+  CHROMEGTK_CALLBACK_1(PanelBrowserTitlebarGtk, gboolean,
+                       OnMinimizeButtonReleaseEvent, GdkEventButton*);
+  CHROMEGTK_CALLBACK_1(PanelBrowserTitlebarGtk, gboolean,
+                       OnUnminimizeButtonReleaseEvent, GdkEventButton*);
+
   PanelBrowserWindowGtk* browser_window_;
 
   // All other buttons, including close and minimize buttons, are defined in