GN: only write targets that should be generated.

tools/gn/builder.h

Index: tools/gn/builder.h
diff --git a/tools/gn/builder.h b/tools/gn/builder.h
index d8209bc048f0729716804a7a66b3741e666287fe..c8b54c9fb1637a06a4e7cd4a5bd6dcac9031fb4a 100644
--- a/tools/gn/builder.h
+++ b/tools/gn/builder.h
@@ -22,15 +22,16 @@ class ParseNode;
 // the main thread only. See also BuilderRecord.
 class Builder {
  public:
-  typedef base::Callback<void(const BuilderRecord*)> ResolvedCallback;
+  typedef base::Callback<void(const BuilderRecord*)> ResolvedGeneratedCallback;
 
   explicit Builder(Loader* loader);
   ~Builder();
 
-  // The resolved callback is called whenever a target has been resolved. This
-  // will be executed only on the main thread.
-  void set_resolved_callback(const ResolvedCallback& cb) {
-    resolved_callback_ = cb;
+  // The resolved callback is called when a target has been both resolved and
+  // marked generated. This will be executed only on the main thread.
+  void set_resolved_and_generated_callback(
+      const ResolvedGeneratedCallback& cb) {
+    resolved_and_generated_callback_ = cb;
   }
 
   Loader* loader() const { return loader_; }
@@ -132,7 +133,7 @@ class Builder {
   typedef base::hash_map<Label, BuilderRecord*> RecordMap;
   RecordMap records_;
 
-  ResolvedCallback resolved_callback_;
+  ResolvedGeneratedCallback resolved_and_generated_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(Builder);
 };