Adding target to build SwiftShader

BUILD.gn

 # 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.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 476 matching lines @@
   }
 
   if (is_ios || is_win || (is_linux && !is_chromeos)) {
     deps += [
       "//base:base_i18n_perftests",
       "//base:base_perftests",
       "//google_apis:google_apis_unittests",
     ]
   }
 
+  # TODO(sugoi) bug 644737: Remove the '!is_clang' condition once __nop is supported by clang-cl
+  if (is_linux || (is_win && !is_clang)) {
+    deps += [ "//third_party/swiftshader" ]
+  }
+
   # TODO(GYP): Figure out which of these should (and can) build
   # for chromeos/ios.
   if (!is_chromeos && !is_ios) {
     deps += [
       "//base:build_utf8_validator_tables",
       "//base:check_example",
       "//cc:cc_perftests",
       "//cc/blink:cc_blink_unittests",
       "//components:components_perftests",
       "//components/sync:run_sync_testserver",
@@ skipping 619 matching lines @@
       "//ui/display:display_unittests",
       "//ui/events:events_unittests",
       "//ui/gfx:gfx_unittests",
       "//ui/gl:gl_unittests",
       "//ui/keyboard:keyboard_unittests",
       "//ui/touch_selection:ui_touch_selection_unittests",
       "//url:url_unittests",
     ]
   }
 }