Move storage tests from content/common next to the files they cover.

storage/browser/BUILD.gn

 # Copyright 2014 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("//testing/test.gni")
 
 component("browser") {
   output_name = "storage_browser"
   sources = [
     "blob/blob_data_builder.cc",
     "blob/blob_data_builder.h",
@@ skipping 204 matching lines @@
 
   deps = [
     ":browser",
     "//base",
     "//build/config/sanitizers:deps",
     "//build/win:default_exe_manifest",
     "//storage/common",
   ]
 }
 
-test("storage_unittests") {
+source_set("unittests") {
+  testonly = true
+
   sources = [
     # This target is in the process of being populated. See
     # http://crbug.com/653751
     "blob/blob_data_builder_unittest.cc",
     "blob/blob_flattener_unittest.cc",
     "blob/blob_memory_controller_unittest.cc",
     "blob/blob_reader_unittest.cc",
     "blob/blob_slice_unittest.cc",
     "blob/blob_storage_context_unittest.cc",
     "blob/blob_storage_registry_unittest.cc",
@@ skipping 90 matching lines @@
   ]
 
   deps = [
     ":browser",
     "//base/test:test_support",
     "//net:test_support",
     "//testing/gtest",
     "//third_party/leveldatabase",
   ]
 }