Allow .o files for GN generated inputs.

tools/gn/target_unittest.cc

Index: tools/gn/target_unittest.cc
diff --git a/tools/gn/target_unittest.cc b/tools/gn/target_unittest.cc
index 4d9b1da8b8fa56c14cf1cac8d12ed9fa9621768d..c59f44c0717de4f6f19fb14df8f18eea98ea5220 100644
--- a/tools/gn/target_unittest.cc
+++ b/tools/gn/target_unittest.cc
@@ -587,6 +587,31 @@ TEST(Target, WriteFileGeneratedInputs) {
   EXPECT_TRUE(scheduler.GetUnknownGeneratedInputs().empty());
 }
 
+// Tests that intermediate object files generated by binary targets are also
+// considered generated for the purposes of input checking. Above, we tested
+// the failure cases for generated inputs, so here only test .o files that are
+// present.
+TEST(Target, ObjectGeneratedInputs) {
+  Scheduler scheduler;
+  TestWithScope setup;
+  Err err;
+
+  // This target compiles the source.
+  SourceFile source_file("//source.cc");
+  TestTarget source_generator(setup, "//:source_target", Target::SOURCE_SET);
+  source_generator.sources().push_back(source_file);
+  EXPECT_TRUE(source_generator.OnResolved(&err));
+
+  // This is the object file that the test toolchain generates for the source.
+  SourceFile object_file("//out/Debug/obj/source_target.source.o");
+
+  TestTarget final_target(setup, "//:final", Target::ACTION);
+  final_target.inputs().push_back(object_file);
+  EXPECT_TRUE(final_target.OnResolved(&err));
+
+  AssertSchedulerHasOneUnknownFileMatching(&final_target, object_file);
+}
+
 TEST(Target, ResolvePrecompiledHeaders) {
   TestWithScope setup;
   Err err;