Add feature flag for new select-to-speak enhancements.

Also exposed in chrome://flags.

Bug: 1142601
Change-Id: I0067a298e160510150dd793830a13837ccc083ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2500261
Reviewed-by: Dominic Mazzoni <[email protected]>
Commit-Queue: Joel Riley <[email protected]>
Cr-Commit-Position: refs/heads/master@{#821487}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 5d53d53..6f82ebe 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -2551,6 +2551,9 @@
 extern const char kSchedulerConfigurationConservative[];
 extern const char kSchedulerConfigurationPerformance[];
 
+extern const char kSelectToSpeakNavigationControlName[];
+extern const char kSelectToSpeakNavigationControlDescription[];
+
 extern const char kSeparatePointingStickSettingsName[];
 extern const char kSeparatePointingStickSettingsDescription[];