Add GN output prefix override and allow empty output extensions.

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 78 matching lines @@
   void set_output_name(const std::string& name) { output_name_ = name; }
 
   // Returns the output name for this target, which is the output_name if
   // specified, or the target label if not. If the flag is set, it will also
   // include any output prefix specified on the tool (often "lib" on Linux).
   //
   // Because this depends on the tool for this target, the toolchain must
   // have been set before calling.
   std::string GetComputedOutputName(bool include_prefix) const;
 
+  bool output_prefix_override() const { return output_prefix_override_; }
+  void set_output_prefix_override(bool prefix_override) {
+    output_prefix_override_ = prefix_override;
+  }
+
+  // The output extension is really a tri-state: unset (output_extension_set
+  // is false and the string is empty, meaning the default extension should be
+  // used), the output extension is set but empty (output should have no
+  // extension) and the output extension is set but nonempty (use the given
+  // extension).
   const std::string& output_extension() const { return output_extension_; }
   void set_output_extension(const std::string& extension) {
     output_extension_ = extension;
+    output_extension_set_ = true;
+  }
+  bool output_extension_set() const {
+    return output_extension_set_;
   }
 
   const FileList& sources() const { return sources_; }
   FileList& sources() { return sources_; }
 
   // Set to true when all sources are public. This is the default. In this case
   // the public headers list should be empty.
   bool all_headers_public() const { return all_headers_public_; }
   void set_all_headers_public(bool p) { all_headers_public_ = p; }
 
@@ skipping 199 matching lines @@
   // Validates the given thing when a target is resolved.
   bool CheckVisibility(Err* err) const;
   bool CheckTestonly(Err* err) const;
   bool CheckNoNestedStaticLibs(Err* err) const;
   bool CheckAssertNoDeps(Err* err) const;
   void CheckSourcesGenerated() const;
   void CheckSourceGenerated(const SourceFile& source) const;
 
   OutputType output_type_;
   std::string output_name_;
+  bool output_prefix_override_;
   std::string output_extension_;
+  bool output_extension_set_;
 
   FileList sources_;
   bool all_headers_public_;
   FileList public_headers_;
   bool check_includes_;
   bool complete_static_lib_;
   bool testonly_;
   FileList inputs_;
   std::vector<std::string> data_;
   BundleData bundle_data_;
@@ skipping 39 matching lines @@
   // Output files. Empty until the target is resolved.
   std::vector<OutputFile> computed_outputs_;
   OutputFile link_output_file_;
   OutputFile dependency_output_file_;
   OutputFile runtime_link_output_file_;
 
   DISALLOW_COPY_AND_ASSIGN(Target);
 };
 
 #endif  // TOOLS_GN_TARGET_H_