[Omnibox] Control phone-tablet layout switching w/ new flag

This lets us roll this out independently of visual changes tied to the
revamp feature flag.

Bug: 1416985, 1213560
Change-Id: Ifb0eb66fc6505d37b933924d8a0dffb86a5dac3d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4301559
Code-Coverage: Findit <[email protected]>
Commit-Queue: Patrick Noland <[email protected]>
Reviewed-by: Tomasz Wiszkowski <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1115447}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index dff225a6..df8b613 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -2034,6 +2034,12 @@
     "flag to adjust the limit of offered suggestions. The number of shown "
     "suggestions will be no less than the platform default limit.";
 
+const char kOmniboxAdaptNarrowTabletWindowsName[] =
+    "Omnibox adapts to narrow tablet windows";
+const char kOmniboxAdaptNarrowTabletWindowsDescription[] =
+    "When enabled the omnibox uses a phone-like appearance for windows that "
+    "are less than 600dp wide, regardless of the overall display width.";
+
 const char kOmniboxAssistantVoiceSearchName[] =
     "Omnibox Assistant Voice Search";
 const char kOmniboxAssistantVoiceSearchDescription[] =