Add GetPersistentSetting() to h5vcc_settings.

Add a persistent settings getter to validate set persistent h5vcc
settings. The getter is a string getter that maps to the various types
that allows for empty string returns when the getter fails.

b/305057554

Change-Id: Iefde82ef3110c0b9c90a45807edd5652ba59ed0b

cobalt/h5vcc/h5vcc_settings.cc

@@ -104,5 +104,24 @@ bool H5vccSettings::Set(const std::string& name, SetValueType value) const {
   return false;
 }
 
+std::string H5vccSettings::GetPersistentSetting(
+    const std::string& name, const std::string& default_setting) const {
+  const char kQUIC[] = "QUIC";
+
+  if (persistent_settings_) {
+    // Accepts the string "true" or "false" as the default setting.
+    // Returns the string "true" or "false".
+    if (name.compare(kQUIC) == 0) {
+      bool value = persistent_settings_->GetPersistentSettingAsBool(
+          network::kQuicEnabledPersistentSettingsKey, default_setting);
+      if (value) {
+        return "true";
+      }
+      return "false";
+    }
+  }
+  return "";
+}
+
 }  // namespace h5vcc
 }  // namespace cobalt

cobalt/h5vcc/h5vcc_settings.h

@@ -58,6 +58,9 @@ class H5vccSettings : public script::Wrappable {
   // invalid or not set to the expected value.
   bool Set(const std::string& name, SetValueType value) const;
 
+  std::string GetPersistentSetting(const std::string& name,
+                                   const std::string& default_setting) const;
+
   DEFINE_WRAPPABLE_TYPE(H5vccSettings);
 
  private:

cobalt/h5vcc/h5vcc_settings.idl

@@ -14,4 +14,5 @@
 
 interface H5vccSettings {
   boolean set(DOMString name, (long or DOMString) value);
+  DOMString getPersistentSetting(DOMString name, DOMString default_setting);
 };