Turn on Sideload Warning UI (Windows only) to gather more data (leaving Sideload Wipeout off).

chrome/common/extensions/feature_switch.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/common/extensions/feature_switch.h"
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "base/metrics/field_trial.h"
 #include "base/string_util.h"
@@ skipping 23 matching lines @@
 #if !defined(OS_MACOSX)
             FeatureSwitch::DEFAULT_ENABLED),
 #else
             FeatureSwitch::DEFAULT_DISABLED),
 #endif
         sideload_wipeout(
             switches::kSideloadWipeout,
             FeatureSwitch::DEFAULT_DISABLED),
         prompt_for_external_extensions(
             switches::kPromptForExternalExtensions,
+#if defined(OS_WIN)
+            FeatureSwitch::DEFAULT_ENABLED),
+#else
             FeatureSwitch::DEFAULT_DISABLED),
+#endif
         tab_capture(
             switches::kTabCapture,
             FeatureSwitch::DEFAULT_ENABLED)
   {
     if (!action_box.IsEnabled()){
       extensions_in_action_box.SetOverrideValue(
           FeatureSwitch::OVERRIDE_DISABLED);
     }
   }
 
@@ skipping 104 matching lines @@
 
 void FeatureSwitch::SetOverrideValue(OverrideValue override_value) {
   override_value_ = override_value;
 }
 
 FeatureSwitch::OverrideValue FeatureSwitch::GetOverrideValue() const {
   return override_value_;
 }
 
 }  // namespace extensions