Make MCP/Thrift ContextProp compatible with lifetime pairing

Summary:
For lifetime pairing requests, Thrift Framework Metadata is currently missing on the WWW side. This diff is a proof-of-concept fix. But ideally we shouldn't be recreating the thrift metadata. I'm fairly confident it is indeed being created from timestamp logs, but it ends up as null when lifetime pairing thrift client is called.

Context(Prop) workplace post: https://fb.workplace.com/groups/515642096314492/posts/1381729806372379

Differential Revision: D73286706

fbshipit-source-id: 7b407bf6ce22901d8453e1066b21c85bac2f6e74

Author: Eddie Ren

third-party/thrift/src/thrift/lib/hack/src/ThriftContextPropState.php

@@ -44,6 +44,23 @@ public static function initFromHeaders()[defaults]: void {
     self::initFromString($tfm, $skip_experiment_id_ingestion);
   }
 
+  /**
+  * Initializes ThriftContextPropState from WWW subrequest Headers.
+  * Takes in custom subrequest headers
+  */
+  public static function getOriginIdFromSubrequestHeaders(
+    HTTPHeaders $headers,
+  )[defaults]: ?int {
+    $tfm = $headers->getHeader(HTTPRequestHeader::THRIFT_FMHK);
+    $skip_experiment_id_ingestion =
+      !JustKnobs::eval('lumos/experimentation:enable_www_experiment_id_api');
+    if ($tfm === null) {
+      return 0;
+    }
+    return
+      self::getTfmFromString($tfm, $skip_experiment_id_ingestion)->origin_id;
+  }
+
   // If anything changes with the ThriftFrameworkMetadata, throw out the
   // serialized representation.
   private function dirty()[write_props]: void {
@@ -100,24 +117,16 @@ public static function initFromString(
   )[defaults]: void {
     try {
       $rid_set = false;
+
       if ($s !== null) {
-        $transport = Base64::decode($s);
-        $buf = new TMemoryBuffer($transport);
-        $prot = new TCompactProtocolAccelerated($buf);
-        $tfm = ThriftFrameworkMetadata::withDefaultValues();
-        $tfm->read($prot);
+        $tfm = self::getTfmFromString($s, $skip_experiment_id_ingestion);
+        self::get()->storage = $tfm;
+        self::get()->dirty();
 
         $rid = $tfm->request_id;
         if ($rid !== null && !Str\is_empty($rid)) {
           $rid_set = true;
         }
-
-        if ($skip_experiment_id_ingestion && $tfm->experiment_ids is nonnull) {
-          $tfm->experiment_ids = vec[];
-        }
-
-        self::get()->storage = $tfm;
-        self::get()->dirty();
       }
     } catch (\Exception $ex) {
       // Swallow the error, rather than nuke the whole request
@@ -132,6 +141,24 @@ public static function initFromString(
     }
   }
 
+  private static function getTfmFromString(
+    string $s,
+    bool $skip_experiment_id_ingestion = true,
+  ): ThriftFrameworkMetadata {
+    $transport = Base64::decode($s);
+    $buf = new TMemoryBuffer($transport);
+    $prot = new TCompactProtocolAccelerated($buf);
+    $tfm = ThriftFrameworkMetadata::withDefaultValues();
+    $tfm->read($prot);
+
+    if ($skip_experiment_id_ingestion && $tfm->experiment_ids is nonnull) {
+      $tfm->experiment_ids = vec[];
+    }
+
+    return $tfm;
+
+  }
+
   // update FB user id from explicit value
   public static function updateFBUserId(?int $fb_user_id, string $src): bool {
     // don't overwrite if TCPS already has a valid fb user id