Support painting panels with chromium themes on 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..feaa72577b6d1a86d9a310ff2479ece5581ab341 100644
--- a/chrome/browser/ui/panels/panel_browser_titlebar_gtk.h
+++ b/chrome/browser/ui/panels/panel_browser_titlebar_gtk.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_UI_PANELS_PANEL_BROWSER_TITLEBAR_GTK_H_
 
 #include "chrome/browser/ui/gtk/browser_titlebar.h"
+#include "ui/gfx/skia_util.h"
 
 class PanelBrowserWindowGtk;
 
@@ -17,6 +18,23 @@ class PanelBrowserTitlebarGtk : public BrowserTitlebar {
 
   void UpdateMinimizeRestoreButtonVisibility();
 
+  // When a panel appears in the same position as the one of the panel being
+  // closed and the cursor stays in the close button, the close button appears
+  // not to be clickable. This is because neither "enter-notify-event" nor
+  // "clicked" event for the new panel gets fired if the mouse does not move.
+  // This creates a bad experience when a user has multiple panels of the same
+  // size (which is typical) and tries closing them all by repeatedly clicking
+  // in the same place on the screen.
+  //
+  // Opened a gtk bug for this -
+  //   https://bugzilla.gnome.org/show_bug.cgi?id=667841
+  void SendEnterNotifyToCloseButtonIfUnderMouse();
+
+  // Overridden from BrowserTitlebar:
+  virtual void UpdateButtonBackground(CustomDrawButton* button) OVERRIDE;
+  virtual void UpdateTitleAndIcon() OVERRIDE;
+  virtual void UpdateTextColor() OVERRIDE;
+
  protected:
   // Overridden from BrowserTitlebar:
   virtual bool BuildButton(const std::string& button_token,
@@ -38,6 +56,8 @@ class PanelBrowserTitlebarGtk : public BrowserTitlebar {
     return unminimize_button_.get();
   }
 
+  SkColor GetTextColor() const;
+
   PanelBrowserWindowGtk* browser_window_;
 
   // All other buttons, including close and minimize buttons, are defined in