Move scoped_observer.h from base_unittests to base. It is not a test.

base/BUILD.gn

 # Copyright (c) 2013 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("//build/config/ui.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
@@ skipping 491 matching lines @@
     "rand_util_nacl.cc",
     "rand_util_posix.cc",
     "rand_util_win.cc",
     "run_loop.cc",
     "run_loop.h",
     "safe_strerror_posix.cc",
     "safe_strerror_posix.h",
     "scoped_generic.h",
     "scoped_native_library.cc",
     "scoped_native_library.h",
+    "scoped_observer.h",
     "sequence_checker.h",
     "sequence_checker_impl.cc",
     "sequence_checker_impl.h",
     "sequenced_task_runner.cc",
     "sequenced_task_runner.h",
     "sequenced_task_runner_helpers.h",
     "sha1.h",
     "sha1_portable.cc",
     "sha1_win.cc",
     "single_thread_task_runner.h",
@@ skipping 649 matching lines @@
     "process/process_metrics_unittest.cc",
     "process/process_metrics_unittest_ios.cc",
     "process/process_util_unittest.cc",
     "process/process_util_unittest_ios.cc",
     "profiler/tracked_time_unittest.cc",
     "rand_util_unittest.cc",
     "numerics/safe_numerics_unittest.cc",
     "scoped_clear_errno_unittest.cc",
     "scoped_generic_unittest.cc",
     "scoped_native_library_unittest.cc",
-    "scoped_observer.h",
     "security_unittest.cc",
     "sequence_checker_unittest.cc",
     "sha1_unittest.cc",
     "stl_util_unittest.cc",
     "strings/nullable_string16_unittest.cc",
     "strings/safe_sprintf_unittest.cc",
     "strings/string16_unittest.cc",
     "strings/stringprintf_unittest.cc",
     "strings/string_number_conversions_unittest.cc",
     "strings/string_piece_unittest.cc",
@@ skipping 238 matching lines @@
       "android/java/templates/NativeLibraries.template",
     ]
     inputs = [
       "android/java/templates/native_libraries_array.h",
     ]
 
     package_name = "org/chromium/base/library_loader"
     include_path = "android/java/templates"
   }
 }