Move some File API backend unit tests next to the files that they cover.

content/test/BUILD.gn

Index: content/test/BUILD.gn
diff --git a/content/test/BUILD.gn b/content/test/BUILD.gn
index a83a4f42aa05755b6881d8efb7fcfaf34c4d7a68..d27b2aa5b250eab4810e98e56221b8f3136a9508 100644
--- a/content/test/BUILD.gn
+++ b/content/test/BUILD.gn
@@ -1077,34 +1077,23 @@ test("content_unittests") {
     "../browser/download/parallel_download_utils_unittest.cc",
     "../browser/download/rate_estimator_unittest.cc",
     "../browser/download/save_package_unittest.cc",
-    "../browser/fileapi/copy_or_move_file_validator_unittest.cc",
     "../browser/fileapi/copy_or_move_operation_delegate_unittest.cc",
     "../browser/fileapi/dragged_file_util_unittest.cc",
     "../browser/fileapi/file_system_context_unittest.cc",
-    "../browser/fileapi/file_system_dir_url_request_job_unittest.cc",
-    "../browser/fileapi/file_system_file_stream_reader_unittest.cc",
     "../browser/fileapi/file_system_operation_impl_unittest.cc",
     "../browser/fileapi/file_system_operation_impl_write_unittest.cc",
     "../browser/fileapi/file_system_operation_runner_unittest.cc",
-    "../browser/fileapi/file_system_quota_client_unittest.cc",
-    "../browser/fileapi/file_system_url_request_job_unittest.cc",
-    "../browser/fileapi/file_writer_delegate_unittest.cc",
     "../browser/fileapi/fileapi_message_filter_unittest.cc",
-    "../browser/fileapi/local_file_util_unittest.cc",
     "../browser/fileapi/mock_file_change_observer.cc",
     "../browser/fileapi/mock_file_change_observer.h",
     "../browser/fileapi/mock_file_update_observer.cc",
     "../browser/fileapi/mock_file_update_observer.h",
     "../browser/fileapi/obfuscated_file_util_unittest.cc",
-    "../browser/fileapi/plugin_private_file_system_backend_unittest.cc",
     "../browser/fileapi/recursive_operation_delegate_unittest.cc",
     "../browser/fileapi/sandbox_database_test_helper.cc",
     "../browser/fileapi/sandbox_database_test_helper.h",
     "../browser/fileapi/sandbox_directory_database_unittest.cc",
-    "../browser/fileapi/sandbox_file_system_backend_delegate_unittest.cc",
-    "../browser/fileapi/sandbox_file_system_backend_unittest.cc",
     "../browser/fileapi/sandbox_origin_database_unittest.cc",
-    "../browser/fileapi/transient_file_util_unittest.cc",
     "../browser/fileapi/upload_file_system_file_element_reader_unittest.cc",
     "../browser/frame_host/ancestor_throttle_unittest.cc",
     "../browser/frame_host/frame_tree_node_blame_context_unittest.cc",