ui: Pass display size by const reference in AddVirtualDisplay

BUG=425060
TEST=Build test.

Review-Url: https://codereview.chromium.org/2152883002
Cr-Commit-Position: refs/heads/master@{#405568}

ui/display/chromeos/display_configurator.cc

@@ -1116,7 +1116,7 @@ void DisplayConfigurator::NotifyPowerStateObservers() {
       Observer, observers_, OnPowerStateChanged(current_power_state_));
 }
 
-int64_t DisplayConfigurator::AddVirtualDisplay(gfx::Size display_size) {
+int64_t DisplayConfigurator::AddVirtualDisplay(const gfx::Size& display_size) {
   if (last_virtual_display_id_ == 0xff) {
     LOG(WARNING) << "Exceeded virtual display id limit";
     return display::Display::kInvalidDisplayID;

ui/display/chromeos/display_configurator.h

@@ -276,7 +276,7 @@ class DISPLAY_EXPORT DisplayConfigurator : public NativeDisplayObserver {
                                   ui::ColorCalibrationProfile new_profile);
 
   // Enables/disables virtual display.
-  int64_t AddVirtualDisplay(gfx::Size display_size);
+  int64_t AddVirtualDisplay(const gfx::Size& display_size);
   bool RemoveVirtualDisplay(int64_t display_id);
 
   // Returns true if there is at least one display on.