[Refactor Xcode Objects] Enable generating per file '--help' compiler flag

tools/gn/xcode_object.h

Index: tools/gn/xcode_object.h
diff --git a/tools/gn/xcode_object.h b/tools/gn/xcode_object.h
index 2ad43cceefc4567abad8d2ca2123794f0c0cf606..576e1dd07f313db256653adb79e056558f794d2f 100644
--- a/tools/gn/xcode_object.h
+++ b/tools/gn/xcode_object.h
@@ -151,10 +151,16 @@ class PBXAggregateTarget : public PBXTarget {
 
 // PBXBuildFile ---------------------------------------------------------------
 
+enum class CompilerFlags {

[sdefresne, 2016/12/19 08:05:36]

nit: move at the top of the file with other enums

[liaoyuke, 2016/12/19 08:17:42]

Done.

+  NONE,
+  HELP,
+};
+
 class PBXBuildFile : public PBXObject {
  public:
   PBXBuildFile(const PBXFileReference* file_reference,
-               const PBXSourcesBuildPhase* build_phase);
+               const PBXSourcesBuildPhase* build_phase,
+               const CompilerFlags compiler_flag);
   ~PBXBuildFile() override;
 
   // PXBObject implementation.
@@ -165,6 +171,7 @@ class PBXBuildFile : public PBXObject {
  private:
   const PBXFileReference* file_reference_;
   const PBXSourcesBuildPhase* build_phase_;
+  const CompilerFlags compiler_flag_;
 
   DISALLOW_COPY_AND_ASSIGN(PBXBuildFile);
 };
@@ -247,7 +254,8 @@ class PBXNativeTarget : public PBXTarget {
                   const PBXFileReference* product_reference);
   ~PBXNativeTarget() override;
 
-  void AddFileForIndexing(const PBXFileReference* file_reference);
+  void AddFileForIndexing(const PBXFileReference* file_reference,
+                          const CompilerFlags compiler_flag);
 
   // PBXObject implementation.
   PBXObjectClass Class() const override;
@@ -271,7 +279,8 @@ class PBXProject : public PBXObject {
              const PBXAttributes& attributes);
   ~PBXProject() override;
 
-  void AddSourceFile(const std::string& source_path);
+  void AddSourceFile(const std::string& source_path,
+                     const CompilerFlags compiler_flag);
   void AddAggregateTarget(const std::string& name,
                           const std::string& shell_script);
   void AddNativeTarget(const std::string& name,