gpu_display: delete unused field and method GpuDisplay::is_x

Change-Id: I5a1e4aa28100bf9d935902bf5040b4e4f6744927
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4777341
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>

gpu_display/src/lib.rs

@@ -321,7 +321,6 @@ pub struct GpuDisplay {
     // are declared [Rust RFC 1857].
     inner: Box<dyn SysDisplayT>,
     wait_ctx: WaitContext<DisplayEventToken>,
-    is_x: bool,
 }
 
 impl GpuDisplay {
@@ -342,7 +341,6 @@ impl GpuDisplay {
                 surfaces: Default::default(),
                 imports: Default::default(),
                 wait_ctx,
-                is_x: true,
             })
         }
         #[cfg(not(feature = "x"))]
@@ -361,15 +359,9 @@ impl GpuDisplay {
             surfaces: Default::default(),
             imports: Default::default(),
             wait_ctx,
-            is_x: false,
         })
     }
 
-    /// Return whether this display is an X display
-    pub fn is_x(&self) -> bool {
-        self.is_x
-    }
-
     fn handle_event_device(&mut self, event_device_id: u32) {
         if let Some(event_device) = self.event_devices.get(&event_device_id) {
             // TODO(zachr): decode the event and forward to the device.

gpu_display/src/sys/unix.rs

@@ -57,7 +57,6 @@ impl UnixGpuDisplayExt for GpuDisplay {
             surfaces: Default::default(),
             imports: Default::default(),
             wait_ctx,
-            is_x: false,
         })
     }
 }

gpu_display/src/sys/windows.rs

@@ -67,7 +67,6 @@ impl WinGpuDisplayExt for GpuDisplay {
             surfaces: Default::default(),
             imports: Default::default(),
             wait_ctx,
-            is_x: false,
         })
     }
 }