On Web, never return a MonitorHandle (#3051)

src/platform_impl/web/event_loop/window_target.rs

@@ -746,7 +746,7 @@ impl<T> EventLoopWindowTarget<T> {
     }
 
     pub fn primary_monitor(&self) -> Option<MonitorHandle> {
-        Some(MonitorHandle)
+        None
     }
 
     pub fn raw_display_handle(&self) -> RawDisplayHandle {

src/platform_impl/web/monitor.rs

@@ -1,3 +1,5 @@
+use std::iter::Empty;
+
 use crate::dpi::{PhysicalPosition, PhysicalSize};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -5,30 +7,27 @@ pub struct MonitorHandle;
 
 impl MonitorHandle {
     pub fn scale_factor(&self) -> f64 {
-        1.0
+        unreachable!()
     }
 
     pub fn position(&self) -> PhysicalPosition<i32> {
-        PhysicalPosition { x: 0, y: 0 }
+        unreachable!()
     }
 
     pub fn name(&self) -> Option<String> {
-        None
+        unreachable!()
     }
 
     pub fn refresh_rate_millihertz(&self) -> Option<u32> {
-        None
+        unreachable!()
     }
 
     pub fn size(&self) -> PhysicalSize<u32> {
-        PhysicalSize {
-            width: 0,
-            height: 0,
-        }
+        unreachable!()
     }
 
-    pub fn video_modes(&self) -> impl Iterator<Item = VideoMode> {
-        std::iter::empty()
+    pub fn video_modes(&self) -> Empty<VideoMode> {
+        unreachable!()
     }
 }
 
@@ -37,18 +36,18 @@ pub struct VideoMode;
 
 impl VideoMode {
     pub fn size(&self) -> PhysicalSize<u32> {
-        unimplemented!();
+        unreachable!();
     }
 
     pub fn bit_depth(&self) -> u16 {
-        unimplemented!();
+        unreachable!();
     }
 
     pub fn refresh_rate_millihertz(&self) -> u32 {
-        32000
+        unreachable!();
     }
 
     pub fn monitor(&self) -> MonitorHandle {
-        MonitorHandle
+        unreachable!();
     }
 }

src/platform_impl/web/window.rs

@@ -274,7 +274,7 @@ impl Inner {
     #[inline]
     pub(crate) fn fullscreen(&self) -> Option<Fullscreen> {
         if self.canvas.borrow().is_fullscreen() {
-            Some(Fullscreen::Borderless(Some(MonitorHandle)))
+            Some(Fullscreen::Borderless(None))
         } else {
             None
         }
@@ -335,7 +335,7 @@ impl Inner {
 
     #[inline]
     pub fn current_monitor(&self) -> Option<MonitorHandle> {
-        Some(MonitorHandle)
+        None
     }
 
     #[inline]
@@ -345,7 +345,7 @@ impl Inner {
 
     #[inline]
     pub fn primary_monitor(&self) -> Option<MonitorHandle> {
-        Some(MonitorHandle)
+        None
     }
 
     #[inline]