Avoid the possibility of future conflict with another address-of-static due to COMDAT folding.

components/user_prefs/user_prefs.cc

Index: components/user_prefs/user_prefs.cc
diff --git a/components/user_prefs/user_prefs.cc b/components/user_prefs/user_prefs.cc
index 123d5572c280857d8fadff5fda2fa1afc6606c90..96866d187a7d1193c738a6f0e23dcb7af5dd41ef 100644
--- a/components/user_prefs/user_prefs.cc
+++ b/components/user_prefs/user_prefs.cc
@@ -14,8 +14,10 @@ namespace components {
 namespace {
 
 void* UserDataKey() {
-  // We just need a unique constant. Use the address of this static member.
-  return reinterpret_cast<void*>(&UserPrefs::Get);
+  // We just need a unique constant. Use the address of a static that
+  // COMDAT folding won't touch in an optimizing linker.
+  static int data_key = 0;
+  return reinterpret_cast<void*>(&data_key);
 }
 
 }  // namespace