fix: build failure when PDF viewer is disabled (#44960)

* fix: unused variable warning when the PDF viewer is disabled

* fix: unused function error  when PDF viewer is disabled

error: unused function ParseManifest [-Werror,-Wunused-function]

shell/browser/extensions/electron_extension_system.cc

@@ -87,6 +87,7 @@ void ElectronExtensionSystem::InitForRegularProfile(bool extensions_enabled) {
   management_policy_ = std::make_unique<ManagementPolicy>();
 }
 
+#if BUILDFLAG(ENABLE_PDF_VIEWER)
 namespace {
 
 std::unique_ptr<base::Value::Dict> ParseManifest(
@@ -103,10 +104,11 @@ std::unique_ptr<base::Value::Dict> ParseManifest(
 }
 
 }  // namespace
+#endif  // if BUILDFLAG(ENABLE_PDF_VIEWER)
 
 void ElectronExtensionSystem::LoadComponentExtensions() {
-  std::string utf8_error;
 #if BUILDFLAG(ENABLE_PDF_VIEWER)
+  std::string utf8_error;
   std::string pdf_manifest_string = pdf_extension_util::GetManifest();
   std::unique_ptr<base::Value::Dict> pdf_manifest =
       ParseManifest(pdf_manifest_string);