[ios] Adds ScopedBlockSwizzler.

ios/chrome/test/base/BUILD.gn

Index: ios/chrome/test/base/BUILD.gn
diff --git a/ios/chrome/test/base/BUILD.gn b/ios/chrome/test/base/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..9c7dffc62278d18017205d233df66c2965b00364
--- /dev/null
+++ b/ios/chrome/test/base/BUILD.gn
@@ -0,0 +1,26 @@
+# 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.
+
+source_set("base") {
+  testonly = true
+  sources = [
+    "scoped_block_swizzler.h",
+    "scoped_block_swizzler.mm",
+  ]
+  deps = [
+    "//base",
+  ]
+}
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "scoped_block_swizzler_unittest.mm",
+  ]
+  deps = [
+    ":base",
+    "//base",
+    "//testing/gtest",
+  ]
+}