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/about_flags.cc b/chrome/browser/about_flags.cc
index 521a96e..e6ba94b9 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -5382,6 +5382,11 @@
     {"webui-dark-mode", flag_descriptions::kWebuiDarkModeName,
      flag_descriptions::kWebuiDarkModeDescription, kOsCrOS,
      FEATURE_VALUE_TYPE(features::kWebUIDarkMode)},
+
+    {"select-to-speak-navigation-control",
+     flag_descriptions::kSelectToSpeakNavigationControlName,
+     flag_descriptions::kSelectToSpeakNavigationControlDescription, kOsCrOS,
+     FEATURE_VALUE_TYPE(features::kSelectToSpeakNavigationControl)},
 #endif  // OS_CHROMEOS
 
     {"autofill-off-no-server-data",