Disable sideload UI bubble on ChromeOS.

chrome/browser/extensions/extension_service.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/browser/extensions/extension_service.h"
 
 #include <algorithm>
 #include <set>
 
 #include "base/basictypes.h"
@@ skipping 1738 matching lines @@
   if (!did_show_alert)
     extension_error_ui_.reset();
 }
 
 bool ExtensionService::PopulateExtensionErrorUI(
     ExtensionErrorUI* extension_error_ui) {
   bool needs_alert = false;
   for (ExtensionSet::const_iterator iter = extensions_.begin();
        iter != extensions_.end(); ++iter) {
     const Extension* e = *iter;
+#if !defined(OS_CHROMEOS)
     if (Extension::IsExternalLocation(e->location())) {
       if (!e->is_hosted_app()) {
         if (!extension_prefs_->IsExternalExtensionAcknowledged(e->id())) {
           extension_error_ui->AddExternalExtension(e->id());
           needs_alert = true;
         }
       }
     }
+#endif
     if (!extension_prefs_->UserMayLoad(e, NULL)) {
       if (!extension_prefs_->IsBlacklistedExtensionAcknowledged(e->id())) {
         extension_error_ui->AddBlacklistedExtension(e->id());
         needs_alert = true;
       }
     }
     if (extension_prefs_->IsExtensionOrphaned(e->id())) {
       if (!extension_prefs_->IsOrphanedExtensionAcknowledged(e->id())) {
         extension_error_ui->AddOrphanedExtension(e->id());
         needs_alert = true;
@@ skipping 870 matching lines @@
     extensions::ExtensionHost* extension_host) {
   if (!extension_host)
     return;
 
 #if !defined(OS_ANDROID)
   extensions::LaunchPlatformApp(extension_host->profile(),
                                 extension_host->extension(),
                                 NULL, FilePath());
 #endif
 }