Fall back to the default favicon on invalid favicon files.

ui/gfx/image/image.cc

Index: ui/gfx/image/image.cc
diff --git a/ui/gfx/image/image.cc b/ui/gfx/image/image.cc
index 9854787733b7cf9029de07fec2ffb50081d147b3..9c709dce545519512899d8dc81ac0d8f292807f2 100644
--- a/ui/gfx/image/image.cc
+++ b/ui/gfx/image/image.cc
@@ -342,9 +342,15 @@ SkBitmap Image::AsBitmap() const {
 }
 
 ImageSkia Image::AsImageSkia() const {
-  return IsEmpty() ? ImageSkia(SkBitmap()) : *ToImageSkia();
+  return IsEmpty() ? ImageSkia() : *ToImageSkia();
 }
 
+#if defined(OS_MACOSX)
+NSImage* Image::AsNSImage() const {
+  return IsEmpty() ? nil : ToNSImage();
+}
+#endif
+
 ImageSkia* Image::CopyImageSkia() const {
   return new ImageSkia(*ToImageSkia());
 }