ui:DisplayChangeObserver: Only fill HDR DisplayColorSpaces if supported

This CL lands a tiny fix in the DisplayChangeObserver's: we should only
fill in the HDR DisplayColorSpaces if the monitor actually supports it.
I just stumbled upon it while debugging the next CL in the chain.

Bug: 958166
Change-Id: I3ee41501c04b692e12e1e96959a0d6cbf3c7489b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2317815
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Reviewed-by: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791406}

ui/display/manager/display_change_observer.cc

@@ -96,7 +96,7 @@ gfx::DisplayColorSpaces FillDisplayColorSpaces(
   gfx::DisplayColorSpaces display_color_spaces(
       gfx::ColorSpace::CreateSRGB(), DisplaySnapshot::PrimaryFormat());
 
-  if (allow_high_bit_depth) {
+  if (allow_high_bit_depth && snapshot_color_space.IsHDR()) {
     constexpr float kSDRJoint = 0.75;
     constexpr float kHDRLevel = 3.0;
     const auto primary_id = snapshot_color_space.GetPrimaryID();