Add input logic fst flag

Add a flag in chrome://flags for tester to enable the new input logic.

TEST=simple chrome

Bug: 937152
Change-Id: I02da9f585bca109b1a415d6a588ed01bc3fef7c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1545723
Commit-Queue: Leo Zhang <[email protected]>
Reviewed-by: Scott Violet <[email protected]>
Cr-Commit-Position: refs/heads/master@{#646733}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 666bdee..d7bd0e90 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1955,6 +1955,9 @@
 extern const char kGestureTypingName[];
 extern const char kGestureTypingDescription[];
 
+extern const char kImeInputLogicFstName[];
+extern const char kImeInputLogicFstDescription[];
+
 extern const char kImeServiceName[];
 extern const char kImeServiceDescription[];