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

tools/gn/functions_target.cc

Index: tools/gn/functions_target.cc
diff --git a/tools/gn/functions_target.cc b/tools/gn/functions_target.cc
index 7a293c7c406f0642734ed802760a74d893510622..f2a46b6efb0d38ea02033dabfe188bf58f9fc85b 100644
--- a/tools/gn/functions_target.cc
+++ b/tools/gn/functions_target.cc
@@ -264,6 +264,27 @@ Value RunBundleData(Scope* scope,
                               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";