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

android_webview/browser/aw_browser_context.cc

Index: android_webview/browser/aw_browser_context.cc
diff --git a/android_webview/browser/aw_browser_context.cc b/android_webview/browser/aw_browser_context.cc
index ab386f6f2d1003b44727cc257d65b1c1f23fc443..5130641997255bf7aa563e414d8822494599e377 100644
--- a/android_webview/browser/aw_browser_context.cc
+++ b/android_webview/browser/aw_browser_context.cc
@@ -269,12 +269,6 @@ void AwBrowserContext::InitUserPrefService() {
   user_prefs::UserPrefs::Set(this, user_pref_service_.get());
 }
 
-std::unique_ptr<content::ZoomLevelDelegate>
-AwBrowserContext::CreateZoomLevelDelegate(
-    const base::FilePath& partition_path) {
-  return nullptr;
-}
-
 base::FilePath AwBrowserContext::GetPath() const {
   return context_storage_path_;
 }