Split //ios/public/provider/chrome/browser/* targets.

ios/public/provider/chrome/browser/signin/BUILD.gn

Index: ios/public/provider/chrome/browser/signin/BUILD.gn
diff --git a/ios/public/provider/chrome/browser/signin/BUILD.gn b/ios/public/provider/chrome/browser/signin/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..902e2734bb11e0151bbd11088a7a9c6d27d62035
--- /dev/null
+++ b/ios/public/provider/chrome/browser/signin/BUILD.gn
@@ -0,0 +1,45 @@
+# 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("signin") {
+  sources = [
+    "chrome_identity.h",
+    "chrome_identity.mm",
+    "chrome_identity_browser_opener.h",
+    "chrome_identity_interaction_manager.h",
+    "chrome_identity_interaction_manager.mm",
+    "chrome_identity_service.h",
+    "chrome_identity_service.mm",
+    "signin_error_provider.h",
+    "signin_error_provider.mm",
+    "signin_resources_provider.h",
+    "signin_resources_provider.mm",
+  ]
+  deps = [
+    "//base",
+  ]
+}
+
+source_set("test_support") {
+  testonly = true
+  sources = [
+    "fake_chrome_identity.h",
+    "fake_chrome_identity.mm",
+    "fake_chrome_identity_interaction_manager.h",
+    "fake_chrome_identity_interaction_manager.mm",
+    "fake_chrome_identity_service.h",
+    "fake_chrome_identity_service.mm",
+    "test_signin_resources_provider.h",
+    "test_signin_resources_provider.mm",
+  ]
+  deps = [
+    "//base",
+    "//google_apis",
+    "//ios/public/provider/chrome/browser",
+    "//ios/public/provider/chrome/browser/signin",
+  ]
+  public_deps = [
+    "//testing/gmock",
+  ]
+}