Enable async mode for DownloadURL drags.

ui/base/dragdrop/os_exchange_data_provider_win.cc

Index: ui/base/dragdrop/os_exchange_data_provider_win.cc
diff --git a/ui/base/dragdrop/os_exchange_data_provider_win.cc b/ui/base/dragdrop/os_exchange_data_provider_win.cc
index 3b614bc15618736b9376ba580eb160c20941be19..d1a96503fd3aab0c19de12feddba3c74b6eed36c 100644
--- a/ui/base/dragdrop/os_exchange_data_provider_win.cc
+++ b/ui/base/dragdrop/os_exchange_data_provider_win.cc
@@ -531,6 +531,9 @@ void OSExchangeDataProviderWin::SetDownloadFileInfo(
       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(
@@ -820,17 +823,17 @@ HRESULT DataObjectImpl::EndOperation(
 }
 
 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;
 }