Move referrer policy to a different field when serializing.

components/sessions/content/content_serialized_navigation_driver.cc

Index: components/sessions/content/content_serialized_navigation_driver.cc
diff --git a/components/sessions/content/content_serialized_navigation_driver.cc b/components/sessions/content/content_serialized_navigation_driver.cc
index 4dd6bd0d5a97162fdca18567b1b3dcc3a52a0b6e..0ec6737238d6143ba51786af3f1e8ebf39b654b3 100644
--- a/components/sessions/content/content_serialized_navigation_driver.cc
+++ b/components/sessions/content/content_serialized_navigation_driver.cc
@@ -11,6 +11,13 @@
 
 namespace sessions {
 
+namespace {
+const int kObsoleteReferrerPolicyAlways = 0;
+const int kObsoleteReferrerPolicyDefault = 1;
+const int kObsoleteReferrerPolicyNever = 2;
+const int kObsoleteReferrerPolicyOrigin = 3;
+}  // namespace
+
 // static
 SerializedNavigationDriver* SerializedNavigationDriver::Get() {
   return ContentSerializedNavigationDriver::GetInstance();
@@ -33,6 +40,45 @@ int ContentSerializedNavigationDriver::GetDefaultReferrerPolicy() const {
   return blink::WebReferrerPolicyDefault;
 }
 
+bool ContentSerializedNavigationDriver::MapReferrerPolicyToOldValues(
+    int referrer_policy,
+    int* mapped_referrer_policy) const {
+  switch (referrer_policy) {
+    case blink::WebReferrerPolicyAlways:
+    case blink::WebReferrerPolicyDefault:
+      // "always" and "default" are the same value in all versions.
+      *mapped_referrer_policy = referrer_policy;
+      return true;
+
+    case blink::WebReferrerPolicyOrigin:
+      // "origin" exists in the old encoding.
+      *mapped_referrer_policy = kObsoleteReferrerPolicyOrigin;
+      return true;
+
+    default:
+      // Everything else is mapped to never.
+      *mapped_referrer_policy = kObsoleteReferrerPolicyNever;
+      return false;
+  }
+}
+
+bool ContentSerializedNavigationDriver::MapReferrerPolicyToNewValues(
+    int referrer_policy,
+    int* mapped_referrer_policy) const {
+  switch (referrer_policy) {
+    case kObsoleteReferrerPolicyAlways:
+    case kObsoleteReferrerPolicyDefault:
+      // "always" and "default" are the same value in all versions.
+      *mapped_referrer_policy = referrer_policy;
+      return true;
+
+    default:
+      // Since we don't know what encoding was used, we map the rest to "never".
+      *mapped_referrer_policy = blink::WebReferrerPolicyNever;
+      return false;
+  }
+}
+
 std::string
 ContentSerializedNavigationDriver::GetSanitizedPageStateForPickle(
     const SerializedNavigationEntry* navigation) const {