ui/base/dragdrop: Remove owns_medium from StorageDataInfo

Currently there is only ui::DataObjectImpl::SetData which sets
|owns_medium|, but it should always be true because of DataObjectimpl
duplicates the medium if |should_release| is false.

Bug: 11078061
Test: Run ui_base_unittests.exe --gtest_filter="OSExchangeDataWinTest.SetData*"
Change-Id: I62125ef6d0c4d5d364deb2deefd8272a973507e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2308637
Commit-Queue: Darwin Huang <huangdarwin@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Reviewed-by: Darwin Huang <huangdarwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793425}

ui/base/dragdrop/os_exchange_data_provider_win.cc

@@ -842,13 +842,12 @@ static void DuplicateMedium(CLIPFORMAT source_clipformat,
 
 DataObjectImpl::StoredDataInfo::StoredDataInfo(const FORMATETC& format_etc,
                                                STGMEDIUM* medium)
-    : format_etc(format_etc), medium(medium), owns_medium(true) {}
+    : format_etc(format_etc), medium(medium) {}
 
 DataObjectImpl::StoredDataInfo::~StoredDataInfo() {
-  if (owns_medium) {
-    ReleaseStgMedium(medium);
-    delete medium;
-  }
+  ReleaseStgMedium(medium);
+  delete medium;
+
   if (downloader.get())
     downloader->Stop();
 }
@@ -992,12 +991,6 @@ HRESULT DataObjectImpl::SetData(
                                                                local_medium);
   info->medium->tymed = format_etc->tymed;
 
-  // Since the medium is copied if |should_release| is false, it should be
-  // released whether that flag is true or not.
-  // TODO(crbug.com/1107806): Remove owns_medium, because its value is always
-  // true.
-  info->owns_medium = true;
-
   // Make newly added data appear first.
   // TODO(dcheng): Make various setters agree whether elements should be
   // prioritized from front to back or back to front.

ui/base/dragdrop/os_exchange_data_provider_win.h

@@ -97,7 +97,6 @@ class DataObjectImpl : public DownloadFileObserver,
   struct StoredDataInfo {
     FORMATETC format_etc;
     STGMEDIUM* medium;
-    bool owns_medium;
     std::unique_ptr<DownloadFileProvider> downloader;
 
     StoredDataInfo(const FORMATETC& format_etc, STGMEDIUM* medium);