Deprecate Shutdown.ShutdownType metric

This CL is deprecating the ShutdownType metrics and prefs value.
The ShutdownType2 is more reliable and doesn't require the value
to be stored in local_state.

Follow-up on: https://chromium-review.googlesource.com/c/chromium/src/+/4742700

OBSOLETE_HISTOGRAMS="Shutdown Metrics V1 are replaced by Shutdown Metrics V2"

Change-Id: Ic7d5b8293d34d4148d7d56fd45d382516404ca71
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4750201
Reviewed-by: Scott Violet <[email protected]>
Reviewed-by: Luc Nguyen <[email protected]>
Commit-Queue: Etienne Bergeron <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1180308}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index befcd701..d09865f 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -956,6 +956,7 @@
 // Deprecated 07/2023.
 const char kShutdownNumProcesses[] = "shutdown.num_processes";
 const char kShutdownNumProcessesSlow[] = "shutdown.num_processes_slow";
+const char kShutdownType[] = "shutdown.type";
 
 // Register local state used only for migration (clearing or moving to a new
 // key).
@@ -1091,6 +1092,7 @@
   // Deprecated 07/2023.
   registry->RegisterIntegerPref(kShutdownNumProcesses, 0);
   registry->RegisterIntegerPref(kShutdownNumProcessesSlow, 0);
+  registry->RegisterIntegerPref(kShutdownType, 0);
 }
 
 // Register prefs used only for migration (clearing or moving to a new key).
@@ -2206,6 +2208,7 @@
   // Added 07/2023.
   local_state->ClearPref(kShutdownNumProcesses);
   local_state->ClearPref(kShutdownNumProcessesSlow);
+  local_state->ClearPref(kShutdownType);
 
   // Please don't delete the following line. It is used by PRESUBMIT.py.
   // END_MIGRATE_OBSOLETE_LOCAL_STATE_PREFS