Dedupe code in SetIdleInstallInfo(), FinishIdleInstallInfo() and OnExtensionInstalled().

chrome/browser/extensions/extension_prefs_unittest.cc

Index: chrome/browser/extensions/extension_prefs_unittest.cc
diff --git a/chrome/browser/extensions/extension_prefs_unittest.cc b/chrome/browser/extensions/extension_prefs_unittest.cc
index 49e450c175e305ba153820e9625f297a122c3e4e..eda6ee4dae4569373444576ab1f002abfabda1bc 100644
--- a/chrome/browser/extensions/extension_prefs_unittest.cc
+++ b/chrome/browser/extensions/extension_prefs_unittest.cc
@@ -608,7 +608,8 @@ class ExtensionPrefsIdleInstallInfo : public ExtensionPrefsTest {
         path, Extension::INTERNAL, manifest, Extension::NO_FLAGS, id, &errors);
     ASSERT_TRUE(extension) << errors;
     ASSERT_EQ(id, extension->id());
-    prefs()->SetIdleInstallInfo(extension.get(), Extension::ENABLED);
+    prefs()->SetIdleInstallInfo(extension.get(), Extension::ENABLED,
+                                syncer::StringOrdinal());
   }
 
   // Verifies that we get back expected idle install information previously