Mark drags starting in web content as tainted to avoid file path forgery

ui/base/dragdrop/gtk_dnd_util.h

Index: ui/base/dragdrop/gtk_dnd_util.h
diff --git a/ui/base/dragdrop/gtk_dnd_util.h b/ui/base/dragdrop/gtk_dnd_util.h
index b07a86dbcbb527420ecbb9f52ce0ae3289b8750a..33ee837c7c12f1e5a266bf8d71b15f0bc0827dd0 100644
--- a/ui/base/dragdrop/gtk_dnd_util.h
+++ b/ui/base/dragdrop/gtk_dnd_util.h
@@ -39,7 +39,11 @@ enum {
 
   // Custom data for web drag/drop.
   CUSTOM_DATA = 1 << 10,
-  INVALID_TARGET = 1 << 11,
+
+  // Tracks if the drag originated from the renderer.
+  RENDERER_TAINT = 1 << 11,
+
+  INVALID_TARGET = 1 << 12,
 };
 
 // Get the atom for a given target (of the above enum type). Will return NULL