Introduce BookmarkClient interface to abstract embedder

chrome/test/base/testing_profile.cc

Index: chrome/test/base/testing_profile.cc
diff --git a/chrome/test/base/testing_profile.cc b/chrome/test/base/testing_profile.cc
index 9d53560c57ad8b041693f9f147d935d116971a2d..5721e4e70f4387ba0bf950a93ba259c8d6cfe795 100644
--- a/chrome/test/base/testing_profile.cc
+++ b/chrome/test/base/testing_profile.cc
@@ -495,7 +495,9 @@ void TestingProfile::DestroyTopSites() {
 static KeyedService* BuildBookmarkModel(content::BrowserContext* context) {
   Profile* profile = static_cast<Profile*>(context);
   BookmarkModel* bookmark_model = new BookmarkModel(profile);
-  bookmark_model->Load(profile->GetIOTaskRunner());
+  bookmark_model->Load(profile->GetIOTaskRunner(),
+                       content::BrowserThread::GetMessageLoopProxyForThread(
+                           content::BrowserThread::UI));
   return bookmark_model;
 }