Add about:flag for Scroll-To-Text

Adding chrome://flag to allow users (particularly on Mobile) to easily
enable and test the feature.

Explainer doc: https://github.com/bokand/ScrollToTextFragment

Bug: 919204
Change-Id: I7220b03e8b884fdd9ca5b0a905e386bc72743eac
Reviewed-on: https://chromium-review.googlesource.com/c/1470735
Reviewed-by: Avi Drissman <[email protected]>
Reviewed-by: Rick Byers <[email protected]>
Commit-Queue: David Bokan <[email protected]>
Cr-Commit-Position: refs/heads/master@{#632206}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 8dd94b9f..ad01b86 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -4201,6 +4201,11 @@
      flag_descriptions::kEnableImplicitRootScrollerDescription, kOsAll,
      FEATURE_VALUE_TYPE(blink::features::kImplicitRootScroller)},
 
+    {"enable-text-fragment-anchor",
+     flag_descriptions::kEnableTextFragmentAnchorName,
+     flag_descriptions::kEnableTextFragmentAnchorDescription, kOsAll,
+     FEATURE_VALUE_TYPE(blink::features::kTextFragmentAnchor)},
+
 #if defined(OS_CHROMEOS)
     {"enable-assistant-stereo-input",
      flag_descriptions::kEnableGoogleAssistantStereoInputName,