Send the proper event time when dispatching mouse event on windows aura.

 * Fixes app_shell_browsertests on windows.

BUG=399363

Review URL: https://codereview.chromium.org/663203006

Cr-Commit-Position: refs/heads/master@{#300591}

ui/platform_window/win/win_window.cc

@@ -107,7 +107,7 @@ void WinWindow::SetCursor(PlatformCursor cursor) {}
 void WinWindow::MoveCursorTo(const gfx::Point& location) {}
 
 LRESULT WinWindow::OnMouseRange(UINT message, WPARAM w_param, LPARAM l_param) {
-  MSG msg = { hwnd(), message, w_param, l_param, 0,
+  MSG msg = { hwnd(), message, w_param, l_param, GetMessageTime(),
               { CR_GET_X_LPARAM(l_param), CR_GET_Y_LPARAM(l_param) } };
   MouseEvent event(msg);
   if (IsMouseEventFromTouch(message))