Add functionality to find xctest files under application target.

tools/gn/xcode_writer.h

 // Copyright 2016 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_XCODE_WRITER_H_
 #define TOOLS_GN_XCODE_WRITER_H_
 
 #include <iosfwd>
 #include <map>
 #include <memory>
@@ skipping 42 matching lines @@
 
   // Filters the list of targets to only return the targets with artifacts
   // usable from Xcode (mostly application bundles). On failure populate |err|
   // and return false.
   static bool FilterTargets(const BuildSettings* build_settings,
                             const std::vector<const Target*>& all_targets,
                             const std::string& dir_filters_string,
                             std::vector<const Target*>* targets,
                             Err* err);
 
+  // Filters list of targets to only return ones that are xctest module bundles.
+  static void FilterXCTestModuleTargets(
+      const std::vector<const Target*>& targets,
+      std::vector<const Target*>* xctest_module_targets);
+
   // Generate the "products.xcodeproj" project that reference all products
   // (i.e. targets that have a build artefact usable from Xcode, mostly
   // application bundles).
   void CreateProductsProject(const std::vector<const Target*>& targets,
                              const PBXAttributes& attributes,
                              const std::string& source_path,
                              const std::string& config_name,
                              const std::string& root_target,
                              const std::string& ninja_extra_args,
                              const BuildSettings* build_settings,
@@ skipping 17 matching lines @@
   void WriteWorkspaceContent(std::ostream& out);
   void WriteProjectContent(std::ostream& out, PBXProject* project);
 
   std::string name_;
   std::vector<std::unique_ptr<PBXProject>> projects_;
 
   DISALLOW_COPY_AND_ASSIGN(XcodeWriter);
 };
 
 #endif  // TOOLS_GN_XCODE_WRITER_H_