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

tools/gn/target.cc

Index: tools/gn/target.cc
diff --git a/tools/gn/target.cc b/tools/gn/target.cc
index 759d7bff14493e59663830c67f2259562eb28f11..b7618dc1933f6ca1e376c1d6eb3b42aa2699ee76 100644
--- a/tools/gn/target.cc
+++ b/tools/gn/target.cc
@@ -422,6 +422,13 @@ DepsIteratorRange Target::GetDeps(DepsIterationType type) const {
     return DepsIteratorRange(DepsIterator(
         &public_deps_, &private_deps_, nullptr));
   }
+  if (type == DEPS_PRIVATE) {
+    return DepsIteratorRange(
+        DepsIterator(&private_deps_, &data_deps_, nullptr));
+  }
+  if (type == DEPS_PUBLIC) {
+    return DepsIteratorRange(DepsIterator(&public_deps_, nullptr, nullptr));
+  }
   // All deps.
   return DepsIteratorRange(DepsIterator(
       &public_deps_, &private_deps_, &data_deps_));