Add the concept of a source set to GN.

tools/gn/ninja_binary_target_writer.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_NINJA_BINARY_TARGET_WRITER_H_
 #define TOOLS_GN_NINJA_BINARY_TARGET_WRITER_H_
 
 #include "base/compiler_specific.h"
 #include "tools/gn/ninja_target_writer.h"
 #include "tools/gn/toolchain.h"
 
 // Writes a .ninja file for a binary target type (an executable, a shared
 // library, or a static library).
 class NinjaBinaryTargetWriter : public NinjaTargetWriter {
  public:
   NinjaBinaryTargetWriter(const Target* target, std::ostream& out);
   virtual ~NinjaBinaryTargetWriter();
 
   virtual void Run() OVERRIDE;
 
  private:
+  typedef std::set<OutputFile> OutputFileSet;
+
   void WriteCompilerVars();
   void WriteSources(std::vector<OutputFile>* object_files);
   void WriteLinkerStuff(const std::vector<OutputFile>& object_files);
   void WriteLinkerFlags();
 
   // Writes the build line for linking the target. Includes newline.
   void WriteLinkCommand(const OutputFile& external_output_file,
                         const OutputFile& internal_output_file,
                         const std::vector<OutputFile>& object_files);
 
+  // Writes the stamp line for a source set. These are not linked.
+  void WriteSourceSetStamp(const std::vector<OutputFile>& object_files);
+
+  // Gets all target dependencies and classifies them, as well as accumulates
+  // object files from source sets we need to link.
+  void GetDeps(std::set<OutputFile>* extra_object_files,
+               std::vector<const Target*>* linkable_deps,
+               std::vector<const Target*>* non_linkable_deps) const;
+
+  // Classifies the dependency as linkable or nonlinkable with the current
+  // target, adding it to the appropriate vector. If the dependency is a source
+  // set we should link in, the source set's object files will be appended to
+  // |extra_object_files|.
+  void ClassifyDependency(const Target* dep,
+                          std::set<OutputFile>* extra_object_files,
+                          std::vector<const Target*>* linkable_deps,
+                          std::vector<const Target*>* non_linkable_deps) const;
+
+  // Writes the implicit dependencies for the link or stamp line. This is
+  // the "||" and everything following it on the ninja line.
+  //
+  // The implicit dependencies are the non-linkable deps passed in as an
+  // argument, plus the data file depdencies in the target.
+  void WriteImplicitDependencies(
+      const std::vector<const Target*>& non_linkable_deps);
+
   Toolchain::ToolType tool_type_;
 
   DISALLOW_COPY_AND_ASSIGN(NinjaBinaryTargetWriter);
 };
 
 #endif  // TOOLS_GN_NINJA_BINARY_TARGET_WRITER_H_