injectContent(contentBlob) {
    if (this.wasDecorated()) {
      throw new Error('Prompt was already decorated.');
    }
    this.injectedContent_ = contentBlob;
  }
Injects a content from external sources (used for popout functionality and
provider-initiated actions). Needs to be called before decorate().
@param {?messages.BridgeMessageRequest} contentBlob The content to process.
@export