aura: Allow platform to choose how it retrieves ICCProfile.

ui/aura/window_tree_host.cc

Index: ui/aura/window_tree_host.cc
diff --git a/ui/aura/window_tree_host.cc b/ui/aura/window_tree_host.cc
index 902d8e94569e13608320f59b23f0c89ac1f39f9e..afa08aa984ee79bb848ff46546305472dfeec3c5 100644
--- a/ui/aura/window_tree_host.cc
+++ b/ui/aura/window_tree_host.cc
@@ -69,11 +69,8 @@ void WindowTreeHost::InitCompositor() {
   compositor_->SetScaleAndSize(GetDeviceScaleFactorFromDisplay(window()),
                                GetBounds().size());
   compositor_->SetRootLayer(window()->layer());
-
-  // TODO(hubbe): Get the color space from the *current* monitor and
-  // update it when window is moved or color space configuration changes.
   compositor_->SetDisplayColorSpace(
-      gfx::ICCProfile::FromBestMonitor().GetColorSpace());
+      GetICCProfileForCurrentDisplay().GetColorSpace());
 }
 
 void WindowTreeHost::AddObserver(WindowTreeHostObserver* observer) {
@@ -313,6 +310,12 @@ void WindowTreeHost::OnHostLostWindowCapture() {
     capture_window->ReleaseCapture();
 }
 
+gfx::ICCProfile WindowTreeHost::GetICCProfileForCurrentDisplay() {
+  // TODO(hubbe): Get the color space from the *current* monitor and
+  // update it when window is moved or color space configuration changes.
+  return gfx::ICCProfile::FromBestMonitor();
+}
+
 ui::EventProcessor* WindowTreeHost::GetEventProcessor() {
   return event_processor();
 }