Reland "Credit card autofill ablation experiment setup"

This is a reland of 3d541cac26d562d9a6f621362faef99d807056f6
Original change's description:
> Credit card autofill ablation experiment setup
>
> This CL is patched from  https://chromium-review.googlesource.com/c/chromium/src/+/615603
> Handling this since Kumar doesn't have enough time to finish this in this week.
>
> Bug:755337
>
> Abalation doc - https://docs.google.com/document/d/1vMGO7sfzYDXpev_5ftyLH-WoKpCHA4I9lVLYuesVT9c/edit?ts=59826c12#heading=h.k6sbad93o9zk
>
> Conditional Metrics to log in control & ablation arm
> >>
> Submitted with suggestion shown (once)
> >>
>
> Change-Id: Ie1be217bc9dfcca36419e6635f9f8459be1ec0b5
> Reviewed-on: https://chromium-review.googlesource.com/711021
> Commit-Queue: Shanfeng Zhang <[email protected]>
> Reviewed-by: Roger McFarlane <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#508441}

Bug: 755337
Change-Id: Ife233986e1f3877cea7cdcc128398c64bb1a8818
Reviewed-on: https://chromium-review.googlesource.com/719411
Reviewed-by: Roger McFarlane <[email protected]>
Commit-Queue: Shanfeng Zhang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#509220}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 54a4950..e7c0f4b 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -180,6 +180,9 @@
 extern const char kEnableAsmWasmName[];
 extern const char kEnableAsmWasmDescription[];
 
+extern const char kEnableAutofillCreditCardAblationExperimentDisplayName[];
+extern const char kEnableAutofillCreditCardAblationExperimentDescription[];
+
 extern const char kEnableAutofillCreditCardBankNameDisplayName[];
 extern const char kEnableAutofillCreditCardBankNameDisplayDescription[];