Do not try to make Chrome default when registering it if it can't be made default unattended.

chrome/installer/setup/install.cc

Index: chrome/installer/setup/install.cc
diff --git a/chrome/installer/setup/install.cc b/chrome/installer/setup/install.cc
index aa789447e8ca09045712fa129d76e0efa8684a5f..fb158cc62716b2a11d625b589ebf605815791a58 100644
--- a/chrome/installer/setup/install.cc
+++ b/chrome/installer/setup/install.cc
@@ -483,17 +483,11 @@ void RegisterChromeOnMachine(const InstallerState& installer_state,
   const string16 chrome_exe(
       installer_state.target_path().Append(installer::kChromeExe).value());
   VLOG(1) << "Registering Chrome as browser: " << chrome_exe;
-  if (make_chrome_default) {
-    if (ShellUtil::CanMakeChromeDefaultUnattended()) {
-      int level = ShellUtil::CURRENT_USER;
-      if (installer_state.system_install())
-        level = level | ShellUtil::SYSTEM_LEVEL;
-      ShellUtil::MakeChromeDefault(dist, level, chrome_exe, true);
-    } else if (IsInteractiveProcess()) {
-      ShellUtil::ShowMakeChromeDefaultSystemUI(dist, chrome_exe);
-    } else {
-      ShellUtil::RegisterChromeBrowser(dist, chrome_exe, string16(), false);
-    }
+  if (make_chrome_default && ShellUtil::CanMakeChromeDefaultUnattended()) {
+    int level = ShellUtil::CURRENT_USER;
+    if (installer_state.system_install())
+      level = level | ShellUtil::SYSTEM_LEVEL;
+    ShellUtil::MakeChromeDefault(dist, level, chrome_exe, true);
   } else {
     ShellUtil::RegisterChromeBrowser(dist, chrome_exe, string16(), false);
   }