Make HistoryBackend a client of memory coordinator

content/browser/memory/memory_coordinator_browsertest.cc

 // 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 "components/memory_coordinator/browser/memory_coordinator.h"
 #include "components/memory_coordinator/common/memory_coordinator_features.h"
 #include "content/browser/browser_main_loop.h"
 #include "content/public/test/content_browser_test.h"
 #include "content/public/test/content_browser_test_utils.h"
 
 namespace content {
 
 class MemoryCoordinatorTest : public ContentBrowserTest {
  public:
   MemoryCoordinatorTest() {}
 
   void SetUp() override {
     memory_coordinator::EnableForTesting();
     ContentBrowserTest::SetUp();
   }
 
  protected:
   memory_coordinator::MemoryCoordinator* memory_coordinator() {
-    return BrowserMainLoop::GetInstance()->memory_coordinator();
+    return memory_coordinator::MemoryCoordinator::GetInstance();
   }
 
   DISALLOW_COPY_AND_ASSIGN(MemoryCoordinatorTest);
 };
 
 IN_PROC_BROWSER_TEST_F(MemoryCoordinatorTest, HandleAdded) {
   GURL url = GetTestUrl("", "simple_page.html");
   NavigateToURL(shell(), url);
   EXPECT_EQ(1u, memory_coordinator()->NumChildrenForTesting());
 }
 
 }  // namespace content