Update browser actions api to be like new design doc.

chrome/browser/gtk/browser_actions_toolbar_gtk.cc

Index: chrome/browser/gtk/browser_actions_toolbar_gtk.cc
diff --git a/chrome/browser/gtk/browser_actions_toolbar_gtk.cc b/chrome/browser/gtk/browser_actions_toolbar_gtk.cc
index cf90faa340e0fbbadd6373d592ca0aded5ce9f95..7347876e6129d48c3cecc73d75292dc3d85cbeee 100644
--- a/chrome/browser/gtk/browser_actions_toolbar_gtk.cc
+++ b/chrome/browser/gtk/browser_actions_toolbar_gtk.cc
@@ -93,7 +93,13 @@ class BrowserActionButton : public NotificationObserver,
 
   // ImageLoadingTracker::Observer implementation.
   void OnImageLoaded(SkBitmap* image, size_t index) {
-    browser_action_icons_[index] = gfx::GdkPixbufFromSkBitmap(image);
+    if (image) {
+      browser_action_icons_[index] = gfx::GdkPixbufFromSkBitmap(image);
+    } else {
+      SkBitmap empty;
+      browser_action_icons_[index] = gfx::GdkPixbufFromSkBitmap(&empty);
+    }
+
     OnStateUpdated();
   }