Gtk3: Fix memory leaks

chrome/browser/ui/libgtkui/gtk_util.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_UI_LIBGTKUI_GTK_UTIL_H_
 #define CHROME_BROWSER_UI_LIBGTKUI_GTK_UTIL_H_
 
 #include <gtk/gtk.h>
 #include <string>
 
@@ skipping 147 matching lines @@
   // a parent whose only reference was the child context in question.
   // This is a hack to work around that case.  See GTK commit
   // "gtkstylecontext: Don't try to emit a signal when finalizing".
   GtkStyleContext* context = obj_;
   while (context) {
     GtkStyleContext* parent = gtk_style_context_get_parent(context);
     if (parent && G_OBJECT(context)->ref_count == 1 &&
         !GtkVersionCheck(3, 15, 4)) {
       g_object_ref(parent);
       gtk_style_context_set_parent(context, nullptr);
+      g_object_unref(context);
     } else {
       g_object_unref(context);
       return;
     }
     context = parent;
   }
 }
 
 typedef ScopedGObject<GtkStyleContext> ScopedStyleContext;
 typedef ScopedGObject<GtkCssProvider> ScopedCssProvider;
@@ skipping 41 matching lines @@
 SkColor GetSelectedTextColor(const char* css_selector);
 SkColor GetSelectedBgColor(const char* css_selector);
 
 // Get the color of the GtkSeparator specified by |css_selector|.
 SkColor GetSeparatorColor(const char* css_selector);
 #endif
 
 }  // namespace libgtkui
 
 #endif  // CHROME_BROWSER_UI_LIBGTKUI_GTK_UTIL_H_