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

ios/chrome/app/application_delegate/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("data_source") {
+source_set("application_delegate") {
   sources = [
-    "physical_web_data_source.cc",
-    "physical_web_data_source.h",
-    "physical_web_data_source_impl.cc",
-    "physical_web_data_source_impl.h",
-    "physical_web_listener.h",
+    "memory_warning_helper.h",
+    "memory_warning_helper.mm",
   ]
-
   deps = [
     "//base",
+    "//ios/chrome/browser/crash_report",
+    "//ios/chrome/browser/metrics",
   ]
+  libs = [ "Foundation.framework" ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
-    "physical_web_data_source_impl_unittest.cc",
+    "memory_warning_helper_unittest.mm",
   ]
-
   deps = [
-    ":data_source",
+    ":application_delegate",
     "//base",
+    "//ios/chrome/browser/metrics",
     "//testing/gtest",
   ]
 }