Enable DPI awareness for util_win service process showing file dialog.

Since https://crrev.com/c/1912502 only enabled DPI awareness for
browser process, this meant utility process showing system UI
was not running at correct DPI.

This adds an explicit call to EnableHighDPISupport in the mojo
IPC to display a file dialog.

BUG=1049324
TEST=Enable high DPI. Load Chrome and push Ctrl-O. Dialog should be shown in High DPI and not blurry.

Change-Id: Ica591e65ba25f3c45485f6676c26436f0d3eb57c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2042744Reviewed-by: Patrick Monette <pmonette@chromium.org>
Commit-Queue: Will Harris <wfh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#739176}

chrome/services/util_win/util_win_impl.cc

@@ -239,6 +239,8 @@ void UtilWinImpl::CallExecuteSelectFile(
     CallExecuteSelectFileCallback callback) {
   base::win::ScopedCOMInitializer scoped_com_initializer;
 
+  base::win::EnableHighDPISupport();
+
   ui::ExecuteSelectFile(
       type, title, default_path, filter, file_type_index, default_extension,
       reinterpret_cast<HWND>(base::win::Uint32ToHandle(owner)),