fix: don't observe WebUSB for in-memory partitions (#42462)

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

shell/browser/hid/electron_hid_delegate.cc

@@ -46,8 +46,8 @@ class ElectronHidDelegate::ContextObservation
   ContextObservation(ElectronHidDelegate* parent,
                      content::BrowserContext* browser_context)
       : parent_(parent), browser_context_(browser_context) {
-    auto* chooser_context = GetChooserContext(browser_context_);
-    device_observation_.Observe(chooser_context);
+    if (auto* chooser_context = GetChooserContext(browser_context_))
+      device_observation_.Observe(chooser_context);
   }
 
   ContextObservation(ContextObservation&) = delete;

shell/browser/usb/electron_usb_delegate.cc

@@ -94,7 +94,8 @@ class ElectronUsbDelegate::ContextObservation
                      content::BrowserContext* browser_context)
       : parent_(parent), browser_context_(browser_context) {
     auto* chooser_context = GetChooserContext(browser_context_);
-    device_observation_.Observe(chooser_context);
+    if (chooser_context)
+      device_observation_.Observe(chooser_context);
   }
   ContextObservation(ContextObservation&) = delete;
   ContextObservation& operator=(ContextObservation&) = delete;