Storage: Re-implement Blob.update_storage_class to support multi-requ…

…est operations

storage/google/cloud/storage/blob.py

@@ -1511,8 +1511,10 @@ def rewrite(self, source, token=None, client=None):
 
         return api_response["rewriteToken"], rewritten, size
 
-    def update_storage_class(self, new_class, client=None, token=None):
-        """Update blob's storage class via a rewrite-in-place.
+    def update_storage_class(self, new_class, client=None):
+        """Update blob's storage class via a rewrite-in-place. This helper will
+        wait for the rewrite to complete before returning, so it may take some
+        time for larger files.
 
         See
         https://cloud.google.com/storage/docs/per-object-storage-class
@@ -1523,26 +1525,22 @@ def update_storage_class(self, new_class, client=None, token=None):
         :type new_class: str
         :param new_class: new storage class for the object
 
-        :type token: str
-        :param token: Optional. Token returned from an earlier, not-completed
-                       call to rewrite the same source blob.  If passed,
-                       result will include updated status, total bytes written.
-
         :type client: :class:`~google.cloud.storage.client.Client`
         :param client: Optional. The client to use.  If not passed, falls back
                        to the ``client`` stored on the blob's bucket.
-
-        :rtype: tuple
-        :returns: See :meth:`~google.cloud.storage.blob.Blob.rewrite` for details.
         """
         if new_class not in self._STORAGE_CLASSES:
             raise ValueError("Invalid storage class: %s" % (new_class,))
 
         # Update current blob's storage class prior to rewrite
         self._patch_property('storageClass', new_class)
 
-        # Use `self` as source blob to rewrite-in-place to the current path
-        return self.rewrite(self, token, client)
+        # Execute consecutive rewrite operations until operation is done
+        token = None
+        while True:
+            token, _, _ = self.rewrite(self, token=token)
+            if token is None:
+                break
 
     cache_control = _scalar_property("cacheControl")
     """HTTP 'Cache-Control' header for this object.