Enable async mode for DownloadURL drags.

ui/base/dragdrop/os_exchange_data_provider_win.cc

 // Copyright (c) 2012 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 "ui/base/dragdrop/os_exchange_data_provider_win.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/files/file_path.h"
@@ skipping 513 matching lines @@
   // think we always synthesize one in WebContentsDragWin.
   STGMEDIUM* storage = NULL;
   if (!download.filename.empty())
     storage = GetStorageForFileName(download.filename);
 
   // Add CF_HDROP.
   DataObjectImpl::StoredDataInfo* info = new DataObjectImpl::StoredDataInfo(
       Clipboard::GetCFHDropFormatType().ToFormatEtc(), storage);
   info->downloader = download.downloader;
   data_->contents_.push_back(info);
+
+  // Adding a download file always enables async mode.
+  data_->SetAsyncMode(VARIANT_TRUE);
 }
 
 void OSExchangeDataProviderWin::SetDragImage(
     const gfx::ImageSkia& image,
     const gfx::Vector2d& cursor_offset) {
   drag_image_ = image;
   drag_image_offset_ = cursor_offset;
 }
 
 const gfx::ImageSkia& OSExchangeDataProviderWin::GetDragImage() const {
@@ skipping 269 matching lines @@
 ///////////////////////////////////////////////////////////////////////////////
 // DataObjectImpl, IDataObjectAsyncCapability implementation:
 
 HRESULT DataObjectImpl::EndOperation(
     HRESULT result, IBindCtx* reserved, DWORD effects) {
   async_operation_started_ = false;
   return S_OK;
 }
 
 HRESULT DataObjectImpl::GetAsyncMode(BOOL* is_op_async) {
-  *is_op_async = in_async_mode_ ? TRUE : FALSE;
+  *is_op_async = in_async_mode_ ? VARIANT_TRUE : VARIANT_FALSE;
   return S_OK;
 }
 
 HRESULT DataObjectImpl::InOperation(BOOL* in_async_op) {
-  *in_async_op = async_operation_started_ ? TRUE : FALSE;
+  *in_async_op = async_operation_started_ ? VARIANT_TRUE : VARIANT_FALSE;
   return S_OK;
 }
 
 HRESULT DataObjectImpl::SetAsyncMode(BOOL do_op_async) {
-  in_async_mode_ = (do_op_async == TRUE);
+  in_async_mode_ = (do_op_async != VARIANT_FALSE);

[dcheng, 2015/04/07 21:04:00]

Even though this is a bit harder to read, I think it's a bit more robust against
people passing in 'incorrect' values of true?

[sadrul, 2015/04/07 21:06:03]

Maybe check for both FALSE and VARIANT_FALSE?

[dcheng, 2015/04/07 21:08:49]

My understanding is VARIANT_FALSE / FALSE / false have the same numerical value,
so this should be OK.

Alternatively, I could just do !!do_op_async. Do we have a pattern for this in
Chrome?

[scottmg, 2015/04/07 21:27:15]

!! is relatively common to convert from BOOL to bool. I think it's OK to rely on
the value of VARIANT_FALSE==FALSE==false==0. (I only mentioned it because
VARIANT_TRUE is -1, not 1, so conceivably something might whine)

[dcheng, 2015/04/07 21:31:00]

I'll just use !! since I find it a bit easier to read personally.

   return S_OK;
 }
 
 HRESULT DataObjectImpl::StartOperation(IBindCtx* reserved) {
   async_operation_started_ = true;
   return S_OK;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 // DataObjectImpl, IUnknown implementation:
@@ skipping 203 matching lines @@
 
 ///////////////////////////////////////////////////////////////////////////////
 // OSExchangeData, public:
 
 // static
 OSExchangeData::Provider* OSExchangeData::CreateProvider() {
   return new OSExchangeDataProviderWin();
 }
 
 }  // namespace ui