GTTF: Enable glibcxx debug mode for Debug builds by default.

ui/gfx/image/image_family.cc

Index: ui/gfx/image/image_family.cc
diff --git a/ui/gfx/image/image_family.cc b/ui/gfx/image/image_family.cc
index 4a43a92e01fe9e9d2139616bae744053c35d3721..6719bc1ab18fc9ecdef4291e7c71d20cb2fa68c9 100644
--- a/ui/gfx/image/image_family.cc
+++ b/ui/gfx/image/image_family.cc
@@ -21,6 +21,8 @@ ImageFamily::const_iterator::const_iterator(
     const std::map<MapKey, gfx::Image>::const_iterator& other)
     : map_iterator_(other) {}
 
+ImageFamily::const_iterator::~const_iterator() {}
+
 ImageFamily::ImageFamily() {}
 ImageFamily::~ImageFamily() {}