refactor: move ElectronExtensionsBrowserClient::PermitExternalProtocolHandler() empty function into header

shell/browser/extensions/electron_extensions_browser_client.cc

@@ -280,8 +280,6 @@ bool ElectronExtensionsBrowserClient::DidVersionUpdate(
   return false;
 }
 
-void ElectronExtensionsBrowserClient::PermitExternalProtocolHandler() {}
-
 bool ElectronExtensionsBrowserClient::IsInDemoMode() {
   return false;
 }

shell/browser/extensions/electron_extensions_browser_client.h

@@ -114,7 +114,7 @@ class ElectronExtensionsBrowserClient
   std::unique_ptr<extensions::ExtensionHostDelegate>
   CreateExtensionHostDelegate() override;
   bool DidVersionUpdate(content::BrowserContext* context) override;
-  void PermitExternalProtocolHandler() override;
+  void PermitExternalProtocolHandler() override {}
   bool IsInDemoMode() override;
   bool IsScreensaverInDemoMode(const std::string& app_id) override;
   bool IsRunningInForcedAppMode() override;