Allow manifest handlers to declare keys they depend on that must be parsed before them.

chrome/common/extensions/extension_unittest.cc

Index: chrome/common/extensions/extension_unittest.cc
diff --git a/chrome/common/extensions/extension_unittest.cc b/chrome/common/extensions/extension_unittest.cc
index e6a891bc0561ba44a06c729b3a3bc62b1d7c6225..9eec106b4c7866ec3bdb97ef00e930efe45426e8 100644
--- a/chrome/common/extensions/extension_unittest.cc
+++ b/chrome/common/extensions/extension_unittest.cc
@@ -126,7 +126,7 @@ class ExtensionTest : public testing::Test {
  protected:
   virtual void SetUp() OVERRIDE {
     ManifestHandler::Register(extension_manifest_keys::kCommands,
-                              new CommandsHandler);
+                              make_linked_ptr(new CommandsHandler));
   }
 };