Do not record extension install histograms for upgrades.

chrome/browser/extensions/extension_service.cc

 // Copyright (c) 2011 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 2037 matching lines @@
     }
   } else {
     // We explicitly want to re-enable an uninstalled external
     // extension; if we're here, that means the user is manually
     // installing the extension.
     if (IsExternalExtensionUninstalled(id)) {
       initial_enable = true;
     }
   }
 
-  UMA_HISTOGRAM_ENUMERATION("Extensions.InstallType",
-                            extension->GetType(), 100);
-  RecordPermissionMessagesHistogram(
-      extension, "Extensions.Permissions_Install");
+  // Do not record the install histograms for upgrades.
+  if (!GetExtensionByIdInternal(extension->id(), true, true, false)) {
+    UMA_HISTOGRAM_ENUMERATION("Extensions.InstallType",
+                              extension->GetType(), 100);
+    RecordPermissionMessagesHistogram(
+        extension, "Extensions.Permissions_Install");
+  }
+
   ShownSectionsHandler::OnExtensionInstalled(profile_->GetPrefs(), extension);
   extension_prefs_->OnExtensionInstalled(
       extension, initial_enable ? Extension::ENABLED : Extension::DISABLED);
 
   // Unpacked extensions default to allowing file access, but if that has been
   // overridden, don't reset the value.
   if (Extension::ShouldAlwaysAllowFileAccess(Extension::LOAD) &&
       !extension_prefs_->HasAllowFileAccessSetting(id)) {
     extension_prefs_->SetAllowFileAccess(id, true);
   }
@@ skipping 344 matching lines @@
 
 ExtensionService::NaClModuleInfoList::iterator
     ExtensionService::FindNaClModule(const GURL& url) {
   for (NaClModuleInfoList::iterator iter = nacl_module_list_.begin();
        iter != nacl_module_list_.end(); ++iter) {
     if (iter->url == url)
       return iter;
   }
   return nacl_module_list_.end();
 }