Convert ios_web_shell_test to GN.

ios/third_party/earl_grey/BUILD.gn

Index: ios/third_party/earl_grey/BUILD.gn
diff --git a/ios/third_party/earl_grey/BUILD.gn b/ios/third_party/earl_grey/BUILD.gn
index c6ab791658f73f129a04d96cd5da01d4afc4ad59..6e95a666f6fdd80f6adc30ba56577b07cc152359 100644
--- a/ios/third_party/earl_grey/BUILD.gn
+++ b/ios/third_party/earl_grey/BUILD.gn
@@ -263,3 +263,16 @@ ios_framework_bundle("earl_grey") {
   configs -= [ "//build/config/gcc:symbol_visibility_hidden" ]
   configs += [ "//build/config/gcc:symbol_visibility_default" ]
 }
+
+bundle_data("xctest_bundle") {
+  testonly = true
+
+  _ios_platform_library = "$ios_sdk_platform_path/Developer/Library"
+  sources = [
+    "$_ios_platform_library/Frameworks/XCTest.framework",

[justincohen, 2016/07/21 18:42:05]

Should this be a part of gn instead of earl grey?  If we ever add other xctests
that aren't earl grey, we will still need this.

[sdefresne, 2016/07/22 13:32:08]

Good idea, I've split the ios_eg_tests in two xctests and eg_tests (with
eg_tests just a wrapper around xctest that add dependencies on earl_grey).

+    "$_ios_platform_library/PrivateFrameworks/IDEBundleInjection.framework",
+  ]
+  outputs = [
+    "{{bundle_resources_dir}}/Frameworks/{{source_file_part}}",
+  ]
+}