Replace "external_install" boolean parameter with explicit enumeration in ExtensionUninstall method.

chrome/browser/extensions/extension_sync_service.cc

Index: chrome/browser/extensions/extension_sync_service.cc
diff --git a/chrome/browser/extensions/extension_sync_service.cc b/chrome/browser/extensions/extension_sync_service.cc
index 7dbe61398620e9c4f501402ea160bd4ed24f164f..a87d855559c9008c97ffaee274ea1f4e66dba103 100644
--- a/chrome/browser/extensions/extension_sync_service.cc
+++ b/chrome/browser/extensions/extension_sync_service.cc
@@ -444,7 +444,10 @@ bool ExtensionSyncService::ProcessExtensionSyncDataHelper(
 
   // Handle uninstalls first.
   if (extension_sync_data.uninstalled()) {
-    if (!extension_service_->UninstallExtensionHelper(extension_service_, id)) {
+    if (!extension_service_->UninstallExtensionHelper(
+            extension_service_,
+            id,
+            ExtensionService::kUninstallReasonSynch)) {
       LOG(WARNING) << "Could not uninstall extension " << id
                    << " for sync";
     }