Add get_target_outputs function to GN

tools/gn/file_template.h

Index: tools/gn/file_template.h
diff --git a/tools/gn/file_template.h b/tools/gn/file_template.h
index d66b3e3c4b6e961fc4f6d53c0e549de83296610b..30b40da6200ced61989e06322f32bb5214a5b025 100644
--- a/tools/gn/file_template.h
+++ b/tools/gn/file_template.h
@@ -14,6 +14,7 @@
 
 struct EscapeOptions;
 class ParseNode;
+class SourceFile;
 class Target;
 
 extern const char kSourceExpansion_Help[];
@@ -61,6 +62,8 @@ class FileTemplate {
   // set. In this case you should not use this object.
   FileTemplate(const Value& t, Err* err);
   FileTemplate(const std::vector<std::string>& t);
+  FileTemplate(const std::vector<SourceFile>& t);
+
   ~FileTemplate();
 
   // Returns an output template representing the given target's script
@@ -80,6 +83,9 @@ class FileTemplate {
              const ParseNode* origin,
              std::vector<Value>* dest,
              Err* err) const;
+
+  // Low-level version of Apply that handles one source file. The results
+  // will be *appended* to the output.
   void ApplyString(const std::string& input,
                    std::vector<std::string>* output) const;