Add the concept of a source set to GN.

tools/gn/target.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/target.h"
 
 #include "base/bind.h"
 #include "tools/gn/config_values_extractors.h"
 #include "tools/gn/scheduler.h"
 
@@ skipping 170 matching lines @@
 void Target::PullDependentTargetInfo(std::set<const Config*>* unique_configs) {
   // Gather info from our dependents we need.
   for (size_t dep_i = 0; dep_i < deps_.size(); dep_i++) {
     const Target* dep = deps_[dep_i];
     MergeAllDependentConfigsFrom(dep, unique_configs, &configs_,
                                  &all_dependent_configs_);
     MergeDirectDependentConfigsFrom(dep, unique_configs, &configs_);
 
     // Direct dependent libraries.
     if (dep->output_type() == STATIC_LIBRARY ||
-        dep->output_type() == SHARED_LIBRARY)
+        dep->output_type() == SHARED_LIBRARY ||
+        dep->output_type() == SOURCE_SET)
       inherited_libraries_.insert(dep);
 
     // Inherited libraries and flags are inherited across static library
     // boundaries. For external targets, assume that the external_link_deps
     // will take care of this.
     if ((!dep->external() ||
          !settings()->build_settings()->using_external_generator()) &&
         dep->output_type() != SHARED_LIBRARY &&
         dep->output_type() != EXECUTABLE) {
       const std::set<const Target*> inherited = dep->inherited_libraries();
@@ skipping 14 matching lines @@
     // The forward_dependent_configs_ must be in the deps already, so we
     // don't need to bother copying to our configs, only forwarding.
     DCHECK(std::find(deps_.begin(), deps_.end(), from_target) !=
            deps_.end());
     const std::vector<const Config*>& direct =
         from_target->direct_dependent_configs();
     for (size_t i = 0; i < direct.size(); i++)
       direct_dependent_configs_.push_back(direct[i]);
   }
 }