Check for inputs not generated by deps

tools/gn/build_settings.h

Index: tools/gn/build_settings.h
diff --git a/tools/gn/build_settings.h b/tools/gn/build_settings.h
index a9752f112448e874b2f319f7f7adebf8f03e704d..f64d5b7518c6414c07e3af39a9e11267dca289cc 100644
--- a/tools/gn/build_settings.h
+++ b/tools/gn/build_settings.h
@@ -94,6 +94,18 @@ class BuildSettings {
     exec_script_whitelist_ = list.Pass();
   }
 
+  // When set (the default), code should perform normal validation of inputs
+  // and structures, like undefined or possibly incorrectly used things. For
+  // some interrogation commands, we don't care about this and actually want
+  // to allow the user to check the structure of the build to solve their
+  // problem, and these checks are undesirable.
+  bool check_for_bad_items() const {
+    return check_for_bad_items_;
+  }
+  void set_check_for_bad_items(bool c) {
+    check_for_bad_items_ = c;
+  }
+
  private:
   base::FilePath root_path_;
   std::string root_path_utf8_;
@@ -109,6 +121,8 @@ class BuildSettings {
 
   scoped_ptr<std::set<SourceFile>> exec_script_whitelist_;
 
+  bool check_for_bad_items_;
+
   BuildSettings& operator=(const BuildSettings& other);  // Disallow.
 };