Downloads: replace BrowserThread::FILE with task scheduler.

content/common/quarantine/quarantine_win.cc

 // 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.
 
 #include "content/public/common/quarantine.h"
 
 #include <windows.h>
 
 #include <cguid.h>
 #include <objbase.h>
 #include <shellapi.h>
 #include <shlobj.h>
 #include <shobjidl.h>
 #include <wininet.h>
 
 #include <vector>
 
 #include "base/files/file_util.h"
 #include "base/guid.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_restrictions.h"
+#include "base/win/scoped_com_initializer.h"
 #include "base/win/scoped_comptr.h"
 #include "base/win/scoped_handle.h"
 #include "url/gurl.h"
 
 namespace content {
 namespace {
 
 // [MS-FSCC] Section 5.6.1
 const base::FilePath::CharType kZoneIdentifierStreamSuffix[] =
     FILE_PATH_LITERAL(":Zone.Identifier");
@@ skipping 257 matching lines @@
 }
 
 }  // namespace
 
 QuarantineFileResult QuarantineFile(const base::FilePath& file,
                                     const GURL& source_url,
                                     const GURL& referrer_url,
                                     const std::string& client_guid) {
   base::ThreadRestrictions::AssertIOAllowed();
 
+  // TODO(siggi): As this is a rare operation, this seems better than putting

[Sigurður Ásgeirsson, 2017/07/20 12:36:34]

Gab: there are two places where downloading needs COM on windows, the other one
is in BaseFile::MoveFileAndAdjustPermissions. I think ideally these would be
invoked on a common/global COM STA thread, but I feel that's outside the scope
of this change. WDYT?

[robliao, 2017/07/20 18:29:17]

I was actually thinking about making ScopedCOMInitializer DCHECK for non COM STA
Task Runners. 

Is it difficult to move this call to a COM STA Task Runner?

[Sigurður Ásgeirsson, 2017/07/20 19:48:15]

I'm not sure, but I'm pretty sure it's out of scope for this CL, which is
already a 6 week drag-on :). I'm more worried that there are untested cases in
downloads that stray into COM or the shell, that I haven't found.

The safe thing to do is to drop downloads on the COM STA sequence on Windows?

[robliao, 2017/07/20 20:15:53]

Dropping all of downloads in a COM STA sounds fine to me.

+  //     all download activity on a COM STA sequence.
+  base::win::ScopedCOMInitializer com_initializer;
+
   int64_t file_size = 0;
   if (!base::PathExists(file) || !base::GetFileSize(file, &file_size))
     return QuarantineFileResult::FILE_MISSING;
 
   std::string braces_guid = "{" + client_guid + "}";
   GUID guid = GUID_NULL;
   if (base::IsValidGUID(client_guid)) {
     HRESULT hr = CLSIDFromString(base::UTF8ToUTF16(braces_guid).c_str(), &guid);
     if (FAILED(hr))
       guid = GUID_NULL;
@@ skipping 28 matching lines @@
   return QuarantineFileResult::OK;
 }
 
 bool IsFileQuarantined(const base::FilePath& file,
                        const GURL& source_url,
                        const GURL& referrer_url) {
   return ZoneIdentifierPresentForFile(file);
 }
 
 }  // namespace content