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..951ec051cef545c93da4685f8b9c906aff4e9ff3 100644
--- a/components/sessions/content/content_serialized_navigation_driver.cc
+++ b/components/sessions/content/content_serialized_navigation_driver.cc
@@ -33,6 +33,41 @@ int ContentSerializedNavigationDriver::GetDefaultReferrerPolicy() const {
   return blink::WebReferrerPolicyDefault;
 }
 
+bool ContentSerializedNavigationDriver::MapReferrerPolicyToOldValues(
+    int referrer_policy,
+    int* mapped_referrer_policy) const {
+  // "always" and "default" are the same value in all versions.
+  if (referrer_policy == blink::WebReferrerPolicyAlways ||
+      referrer_policy == blink::WebReferrerPolicyDefault) {
+    *mapped_referrer_policy = referrer_policy;
+    return true;
+  }
+
+  // "origin" exists in the old encoding.
+  if (referrer_policy == blink::WebReferrerPolicyOrigin) {
+    *mapped_referrer_policy = 3;
+    return true;
+  }
+
+  // Everything else is mapped to never.
+  *mapped_referrer_policy = 2;
+  return false;
+}
+
+bool ContentSerializedNavigationDriver::MapReferrerPolicyToNewValues(
+    int referrer_policy,
+    int* mapped_referrer_policy) const {
+  // "always" and "default" are the same value in all versions.
+  if (referrer_policy == 0 || referrer_policy == 1) {
+    *mapped_referrer_policy = referrer_policy;
+    return true;
+  }
+
+  // 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 {