Add the concept of a source set to GN.

tools/gn/target.h

 // 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.
 
 #ifndef TOOLS_GN_TARGET_H_
 #define TOOLS_GN_TARGET_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 14 matching lines @@
 class Token;
 
 class Target : public Item {
  public:
   enum OutputType {
     UNKNOWN,
     GROUP,
     EXECUTABLE,
     SHARED_LIBRARY,
     STATIC_LIBRARY,
+    SOURCE_SET,
     COPY_FILES,
     CUSTOM,
   };
   typedef std::vector<SourceFile> FileList;
   typedef std::vector<std::string> StringVector;
 
   Target(const Settings* settings, const Label& label);
   virtual ~Target();
 
   // Returns a string naming the output type.
@@ skipping 123 matching lines @@
   std::vector<const Target*> deps_;
   std::vector<const Target*> datadeps_;
 
   std::vector<const Config*> configs_;
   std::vector<const Config*> all_dependent_configs_;
   std::vector<const Config*> direct_dependent_configs_;
   std::vector<const Target*> forward_dependent_configs_;
 
   bool external_;
 
-  // Libraries from transitive deps. Libraries need to be linked only
-  // with the end target (executable, shared library). These do not get
-  // pushed beyond shared library boundaries.
+  // Static libraries and source sets from transitive deps. These things need
+  // to be linked only with the end target (executable, shared library). These
+  // do not get pushed beyond shared library boundaries.
   std::set<const Target*> inherited_libraries_;
 
   // These libs and dirs are inherited from statically linked deps and all
   // configs applying to this target.
   OrderedSet<SourceDir> all_lib_dirs_;
   OrderedSet<std::string> all_libs_;
 
   ConfigValues config_values_;  // Used for all binary targets.
   ScriptValues script_values_;  // Used for script (CUSTOM) targets.
 
   SourceDir destdir_;
 
   bool generated_;
   const Token* generator_function_;  // Who generated this: for error messages.
 
   DISALLOW_COPY_AND_ASSIGN(Target);
 };
 
 #endif  // TOOLS_GN_TARGET_H_