[lensoverlay][reland]Add cursor tooltip and update initial toast string

The original cl was reverted in
I28410d2998da1d1e96a0eaae8fd2199fb8fa174f, but for unrelated tests,
so this cl does not have any test fixes.

One thing this this cl changes from the original is that it hides the
tooltip when the cursor is hovering above a button at the top right.

Also, fixes a small issue where the mouse icon would appear in the top
left corner before moving to the mouse upon mouse move.

Demo: http://screencast/cast/NTQ1MTQ0NzIyMjE0MDkyOHwwYjY0NDFkMC1iNg

Bug: 337943205, 340285304
Change-Id: I8a34ca94300705f130abf76ac1d20fce5abc01a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5548670
Commit-Queue: Jason Hu <[email protected]>
Reviewed-by: Bryan Nguyen <[email protected]>
Reviewed-by: Erik Chen <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1303059}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 69701f6..975d74c 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -2323,6 +2323,8 @@
 #if !BUILDFLAG(IS_ANDROID)
   registry->RegisterIntegerPref(prefs::kChromeDataRegionSetting, 0);
 #endif
+
+  registry->RegisterIntegerPref(prefs::kLensOverlayStartCount, 0);
 }
 
 void RegisterUserProfilePrefs(user_prefs::PrefRegistrySyncable* registry) {