Fall back to existing permission prompt when there's no chip string.

When the Permission Chip is enabled, you get a broken-looking UI when
there's no short string written. This patch works around this by falling
back to the old UI.

Bug: 1019129
Change-Id: If214734f780a0423c4ef9bdb0198c433cffc3cae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2431429
Commit-Queue: Balazs Engedy <[email protected]>
Reviewed-by: Balazs Engedy <[email protected]>
Cr-Commit-Position: refs/heads/master@{#811075}
diff --git a/components/permissions/permission_request.h b/components/permissions/permission_request.h
index 20bedc7..64358a5 100644
--- a/components/permissions/permission_request.h
+++ b/components/permissions/permission_request.h
@@ -6,6 +6,7 @@
 #define COMPONENTS_PERMISSIONS_PERMISSION_REQUEST_H_
 
 #include "base/macros.h"
+#include "base/optional.h"
 #include "base/strings/string16.h"
 #include "build/build_config.h"
 #include "components/content_settings/core/common/content_settings_types.h"
@@ -115,7 +116,7 @@
 
 #if !defined(OS_ANDROID)
   // Returns the short text for the chip button related to this permission.
-  virtual base::string16 GetChipText() const;
+  virtual base::Optional<base::string16> GetChipText() const;
 #endif
 
   // Returns the shortened prompt text for this permission. The permission