Cleanup: Remove references to tests that no longer exists / are unused.

chrome/browser/search/most_visited_iframe_source_unittest.cc

-// Copyright 2013 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 "base/bind.h"
-#include "base/metrics/histogram.h"
-#include "base/metrics/statistics_recorder.h"
-#include "base/strings/stringprintf.h"
-#include "chrome/browser/search/most_visited_iframe_source.h"
-#include "testing/gtest/include/gtest/gtest.h"
-
-class MostVisitedIframeSourceTest : public testing::Test {
- public:
-  void ExpectNullData(base::RefCountedMemory* data) {
-    EXPECT_EQ(NULL, data);
-  }
-
- protected:
-  MostVisitedIframeSource* source() { return source_.get(); }
-
- private:
-  void SetUp() override { source_.reset(new MostVisitedIframeSource()); }
-
-  scoped_ptr<MostVisitedIframeSource> source_;
-};