Add testing/iossim/BUILD.gn to build iossim as host for iOS build.

testing/iossim/BUILD.gn

Index: testing/iossim/BUILD.gn
diff --git a/testing/iossim/BUILD.gn b/testing/iossim/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..a31fdcbfae09d7c4594c035e4c8386b934936938
--- /dev/null
+++ b/testing/iossim/BUILD.gn
@@ -0,0 +1,56 @@
+# 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.
+
+import("//build/config/mac/mac_sdk.gni")
+import("//third_party/class-dump/class-dump.gni")
+
+config("config") {
+  visibility = [ ":iossim" ]
+
+  include_dirs = [ "$root_gen_dir/iossim" ]
+
+  # TODO(crbug.com/595295): Building class-dump tools requires OS X SDK
+  # version 10.9 or higher. Remove this override once the global version
+  # of the SDK is raised.
+  common_flags = [ "-mmacosx-version-min=10.9" ]
+  ldflags = common_flags
+  cflags_objcc = common_flags
+}
+
+executable("iossim") {
+  sources = [
+    "iossim.mm",
+  ]
+  libs = [ "Foundation.framework" ]
+  deps = [
+    ":generate_dvt_core_simulator",
+    ":generate_dvt_foundation_header",
+    ":generate_dvt_iphone_sim_header",
+  ]
+  configs += [ ":config" ]
+
+  # TODO(crbug.com/595295): Building class-dump tools requires OS X SDK
+  # version 10.9 or higher. To prevent mixing code using different value
+  # of minimum SDK supported, forbids dependencies on any Chromium target.
+  assert_no_deps = [ "//base/*" ]
+}
+
+class_dump("generate_dvt_core_simulator") {
+  framework_name = "CoreSimulator"
+  framework_path = "$mac_sdk_path/../../../../../Library/PrivateFrameworks"
+  class_dump_filter = "Sim"
+}
+
+class_dump("generate_dvt_foundation_header") {
+  framework_name = "DVTFoundation"
+  framework_path = "$mac_sdk_path/../../../../../../SharedFrameworks"
+  class_dump_filter = "DVTStackBacktrace|DVTInvalidation|DVTMixIn"
+}
+
+class_dump("generate_dvt_iphone_sim_header") {
+  topological_sort = true
+  framework_name = "DVTiPhoneSimulatorRemoteClient"
+  framework_path = "$mac_sdk_path/../../../../../../SharedFrameworks"
+  class_dump_filter = "iPhoneSimulator"
+}