Split //ios/chrome/browser in multiple targets.

ios/chrome/browser/ssl/BUILD.gn

+# 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("ssl") {
+  sources = [
+    "ios_chrome_security_state_model_client.h",
+    "ios_chrome_security_state_model_client.mm",
+    "ios_ssl_blocking_page.h",
+    "ios_ssl_blocking_page.mm",
+    "ios_ssl_error_handler.h",
+    "ios_ssl_error_handler.mm",
+  ]
+  deps = [
+    "//base",
+    "//components/security_interstitials/core",
+    "//components/security_state",
+    "//components/strings",
+    "//ios/chrome/app/strings",
+    "//ios/chrome/browser/browser_state",
+    "//ios/chrome/browser/interstitials",
+    "//ios/public/provider/chrome/browser",
+    "//ios/web",
+    "//net",
+    "//ui/base",
+    "//url",
+  ]
+}
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "ios_ssl_error_handler_unittest.mm",
+  ]
+  deps = [
+    ":ssl",
+    "//ios/chrome/browser/browser_state:test_support",
+    "//ios/web",
+    "//ios/web:test_support",
+    "//net",
+    "//net:test_support",
+  ]
+}