[ios] Adds test provider implementations.

ios/public/provider/chrome/browser/sessions/test_live_tab_context_provider.cc

Index: ios/public/provider/chrome/browser/sessions/test_live_tab_context_provider.cc
diff --git a/ios/public/provider/chrome/browser/sessions/test_live_tab_context_provider.cc b/ios/public/provider/chrome/browser/sessions/test_live_tab_context_provider.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8a2a4aa86aa26d7392cc36d35528b39ec42b8da6
--- /dev/null
+++ b/ios/public/provider/chrome/browser/sessions/test_live_tab_context_provider.cc
@@ -0,0 +1,20 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ios/public/provider/chrome/browser/sessions/test_live_tab_context_provider.h"
+
+sessions::LiveTabContext* TestLiveTabContextProvider::Create(
+    ios::ChromeBrowserState* browser_state) {
+  return nullptr;
+}
+
+sessions::LiveTabContext* TestLiveTabContextProvider::FindContextWithID(
+    int32_t desired_id) {
+  return nullptr;
+}
+
+sessions::LiveTabContext* TestLiveTabContextProvider::FindContextForTab(
+    const sessions::LiveTab* tab) {
+  return nullptr;
+}