net: Remove unused NetLog parameter from FileStream's ctor

Remove NetLog parameter from FileStream's ctor to which all users are passing NULL.
Remove BoundNetLog from FileStream which does nothing if net_log==NULL.

Remove an enum (FileErrorSource), methods (RecordError, BeginOpenEvent, ProcessOpenError, ProcessAsyncResult, OnAsyncCompleted) and member variables (bound_net_log_ and error_source_) from file_stream_context.h.

BUG=361496
TEST=git cl try

Review URL: https://codereview.chromium.org/242873003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@265576 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/chromeos/drive/local_file_reader.cc b/chrome/browser/chromeos/drive/local_file_reader.cc
index 062bbb8e..e6bacc1d 100644
--- a/chrome/browser/chromeos/drive/local_file_reader.cc
+++ b/chrome/browser/chromeos/drive/local_file_reader.cc
@@ -16,7 +16,7 @@
 
 LocalFileReader::LocalFileReader(
     base::SequencedTaskRunner* sequenced_task_runner)
-    : file_stream_(NULL, sequenced_task_runner),
+    : file_stream_(sequenced_task_runner),
       weak_ptr_factory_(this) {
 }