Add "create_bundle" target in order to support bundle with gn.

tools/gn/functions_target.cc

 // 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.
 
 #include "tools/gn/functions.h"
 
 #include "tools/gn/config_values_generator.h"
 #include "tools/gn/err.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scope.h"
@@ skipping 246 matching lines @@
 
 Value RunBundleData(Scope* scope,
                     const FunctionCallNode* function,
                     const std::vector<Value>& args,
                     BlockNode* block,
                     Err* err) {
   return ExecuteGenericTarget(functions::kBundleData, scope, function, args,
                               block, err);
 }
 
+// create_bundle ---------------------------------------------------------------
+
+const char kCreateBundle[] = "create_bundle";
+const char kCreateBundle_HelpShort[] =
+    "create_bundle: Build an OS X / iOS bundle.";
+const char kCreateBundle_Help[] =
+    "create_bundle: Build an OS X / iOS bundle.\n"
+    "\n"
+    "  This target create an OS X / iOS bundle copying file listed as sources\n"

[brettw, 2016/03/02 21:12:42]

This sentence doesn't make sense to me. Can you expand on this a lot? (It should
be aimed at people that don't understand Mac bundles at all).

We should also be explicit about what platforms this works on and when it
applies. It looks currently like this does something on all platforms, and
requires that the tool exists, so it would normally be inside a mac/iOS
conditional).

[sdefresne, 2016/03/07 20:47:35]

Done.

+    "  of any \"bundle_data\" target it recursively depends (stopping at any\n"
+    "  \"create_bundle\" target).\n";

[brettw, 2016/03/02 21:12:42]

The other target types have a variable section at the bottom for what they read.
Can you add this to here and to bundle_data above and also mark which ones are
required? Like:

  "Variables\n"
  "\n"
  "bundle_root_dir (required), bundle_resources_dir\n" ...

[sdefresne, 2016/03/07 20:47:35]

Done.

+
+Value RunCreateBundle(Scope* scope,
+                      const FunctionCallNode* function,
+                      const std::vector<Value>& args,
+                      BlockNode* block,
+                      Err* err) {
+  return ExecuteGenericTarget(functions::kCreateBundle, scope, function, args,
+                              block, err);
+}
+
 // copy ------------------------------------------------------------------------
 
 const char kCopy[] = "copy";
 const char kCopy_HelpShort[] =
     "copy: Declare a target that copies files.";
 const char kCopy_Help[] =
     "copy: Declare a target that copies files.\n"
     "\n"
     "File name handling\n"
     "\n"
@@ skipping 301 matching lines @@
   const Template* templ = scope->GetTemplate(target_type);
   if (templ)
     return templ->Invoke(scope, function, sub_args, block, err);
 
   // Otherwise, assume the target is a built-in target type.
   return ExecuteGenericTarget(target_type.c_str(), scope, function, sub_args,
                               block, err);
 }
 
 }  // namespace functions