Add display refresh rate to about://gpu on Chrome OS

Some gpu bugs are related to the monitor refresh rate. Adding this display
information will help us on gpu debugging.

Bug: 964095
Change-Id: I54d468dd192110a77f2aa46f7d441ed257f06491
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1644232Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Commit-Queue: Maggie Chen <magchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666313}

ui/display/manager/display_manager.cc

@@ -2098,6 +2098,7 @@ Display DisplayManager::CreateDisplayFromDisplayInfoById(int64_t id) {
   new_display.set_touch_support(display_info.touch_support());
   new_display.set_maximum_cursor_size(display_info.maximum_cursor_size());
   new_display.SetColorSpaceAndDepth(display_info.color_space());
+  new_display.set_display_frequency(display_info.refresh_rate());
 
   if (internal_display_has_accelerometer_ && Display::IsInternalDisplayId(id)) {
     new_display.set_accelerometer_support(