Change default Omaha installsource param from "" to "ondemand"

chrome/browser/extensions/webstore_installer.cc

Index: chrome/browser/extensions/webstore_installer.cc
diff --git a/chrome/browser/extensions/webstore_installer.cc b/chrome/browser/extensions/webstore_installer.cc
index b0573eb70caebb0f36577b494904651334589ec4..453b45744b8de3e3d228b525d6b52a0099de2a67 100644
--- a/chrome/browser/extensions/webstore_installer.cc
+++ b/chrome/browser/extensions/webstore_installer.cc
@@ -66,7 +66,7 @@ const char kInstallCanceledError[] = "Install canceled";
 const char kDownloadInterruptedError[] = "Download interrupted";
 const char kInvalidDownloadError[] = "Download was not a CRX";
 const char kInlineInstallSource[] = "inline";
-const char kDefaultInstallSource[] = "";
+const char kDefaultInstallSource[] = "ondemand";
 
 base::FilePath* g_download_directory_for_tests = NULL;