Don't compile code for desktop zoom or GuestViews on mobile platforms.

content/public/browser/BUILD.gn

Index: content/public/browser/BUILD.gn
diff --git a/content/public/browser/BUILD.gn b/content/public/browser/BUILD.gn
index 2775d680d71f7e2f18b4eea5e872c9d73a4a0345..a6ac68b8ca8d842bc99b518e73d1270bca857fb1 100644
--- a/content/public/browser/BUILD.gn
+++ b/content/public/browser/BUILD.gn
@@ -128,7 +128,6 @@ source_set("browser_sources") {
     "guest_mode.cc",
     "guest_mode.h",
     "histogram_fetcher.h",
-    "host_zoom_map.h",
     "indexed_db_context.h",
     "indexed_db_info.h",
     "interstitial_page.h",
@@ -284,7 +283,6 @@ source_set("browser_sources") {
     "websocket_handshake_request_info.h",
     "worker_service.h",
     "worker_service_observer.h",
-    "zoom_level_delegate.h",
     "zygote_handle_linux.h",
     "zygote_host_linux.h",
   ]
@@ -340,6 +338,10 @@ source_set("browser_sources") {
   }
 
   if (!is_android) {
-    sources += [ "devtools_frontend_host.h" ]
+    sources += [
+      "devtools_frontend_host.h",
+      "host_zoom_map.h",
+      "zoom_level_delegate.h",
+    ]
   }
 }