Implement basic theming for panel titlebars.

chrome/browser/ui/panels/panel_window_controller_cocoa.mm

Index: chrome/browser/ui/panels/panel_window_controller_cocoa.mm
diff --git a/chrome/browser/ui/panels/panel_window_controller_cocoa.mm b/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
index d48f204f791c34606f217a459d1b3d728ee1b427..a9fd1d53552085d8d5f2b1969d84f68ac1fdf225 100644
--- a/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
+++ b/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
@@ -10,6 +10,8 @@
 #include "base/mac/mac_util.h"
 #include "chrome/app/chrome_command_ids.h"  // IDC_*
 #include "chrome/browser/tabs/tab_strip_model.h"
+#include "chrome/browser/themes/theme_service.h"
+#include "chrome/browser/themes/theme_service_factory.h"
 #include "chrome/browser/ui/browser.h"
 #import "chrome/browser/ui/cocoa/event_utils.h"
 #import "chrome/browser/ui/cocoa/find_bar/find_bar_bridge.h"
@@ -32,6 +34,10 @@ const int kMinimumWindowSize = 1;
   return self;
 }
 
+- (ui::ThemeProvider*)themeProvider {
+  return ThemeServiceFactory::GetForProfile(windowShim_->browser()->profile());
+}
+
 - (void)awakeFromNib {
   NSWindow* window = [self window];