gn desc: printing public_deps without --all and --tree

tools/gn/target.h

Index: tools/gn/target.h
diff --git a/tools/gn/target.h b/tools/gn/target.h
index 1890a535e7a7f4c8671ee7be9138e488ce92e1f1..75eadfc267eca1f84ee9cf7dc5cfa4bb9677061f 100644
--- a/tools/gn/target.h
+++ b/tools/gn/target.h
@@ -48,8 +48,10 @@ class Target : public Item {
   };
 
   enum DepsIterationType {
-    DEPS_ALL,  // Iterates through all public, private, and data deps.
-    DEPS_LINKED,  // Iterates through all non-data dependencies.
+    DEPS_ALL,      // Iterates through all public, private, and data deps.
+    DEPS_LINKED,   // Iterates through all non-data dependencies.
+    DEPS_PRIVATE,  // Iterates through private and data deps.
+    DEPS_PUBLIC,   // Iterates through public deps.
   };
 
   typedef std::vector<SourceFile> FileList;