ui/gfx: Make use of SkAutoLockPixels to automatically lock and unlock bitmap pixels properly.

ui/gfx/gtk_util.cc

Index: ui/gfx/gtk_util.cc
diff --git a/ui/gfx/gtk_util.cc b/ui/gfx/gtk_util.cc
index 0b133cb664c4c15c61ee9d372c0fa3215df69cd9..b09975f26435614f3913b0eed3fa98e3d1d434a3 100644
--- a/ui/gfx/gtk_util.cc
+++ b/ui/gfx/gtk_util.cc
@@ -82,7 +82,7 @@ GdkPixbuf* GdkPixbufFromSkBitmap(const SkBitmap* bitmap) {
   if (bitmap->isNull())
     return NULL;
 
-  bitmap->lockPixels();
+  SkAutoLockPixels lock_pixels(*bitmap);
 
   int width = bitmap->width();
   int height = bitmap->height();
@@ -122,7 +122,6 @@ GdkPixbuf* GdkPixbufFromSkBitmap(const SkBitmap* bitmap) {
       8,
       width, height, stride, &FreePixels, divided);
 
-  bitmap->unlockPixels();
   return pixbuf;
 }