Support blob streaming for file-like objects

When uploading file-like objects without a specified size, upload in chunks instead of exhausting the stream and keeping the data in-memory

gcloud/storage/blob.py

@@ -492,9 +492,7 @@ def upload_from_file(self, file_obj, rewind=False, size=None,
         if total_bytes is None:
             if hasattr(file_obj, 'fileno'):
                 total_bytes = os.fstat(file_obj.fileno()).st_size
-            else:
-                raise ValueError('total bytes could not be determined. Please '
-                                 'pass an explicit size.')
+
         headers = {
             'Accept': 'application/json',
             'Accept-Encoding': 'gzip, deflate',
@@ -510,6 +508,12 @@ def upload_from_file(self, file_obj, rewind=False, size=None,
         if self.chunk_size is not None:
             upload.chunksize = self.chunk_size
 
+            if total_bytes is None:
+                upload.strategy = RESUMABLE_UPLOAD
+        elif self.chunk_size is None and total_bytes is None:
+            raise ValueError('total bytes could not be determined. Please '
+                             'pass an explicit size, or supply a chunk size for a streaming transfer.')
+
         url_builder = _UrlBuilder(bucket_name=self.bucket.name,
                                   object_name=self.name)
         upload_config = _UploadConfig()
@@ -522,6 +526,7 @@ def upload_from_file(self, file_obj, rewind=False, size=None,
         # Use apitools 'Upload' facility.
         request = Request(upload_url, 'POST', headers)
 
+
         upload.configure_request(upload_config, request, url_builder)
         query_params = url_builder.query_params
         base_url = connection.API_BASE_URL + '/upload'