Move memory_coordinator_client and its registry to base/memory

components/history/core/browser/history_backend.cc

Index: components/history/core/browser/history_backend.cc
diff --git a/components/history/core/browser/history_backend.cc b/components/history/core/browser/history_backend.cc
index f9e2b57d30b84da86b32032e04514abc76979d12..0b697bde970d8b9d2646443dca9d052ca7511128 100644
--- a/components/history/core/browser/history_backend.cc
+++ b/components/history/core/browser/history_backend.cc
@@ -39,7 +39,6 @@
 #include "components/history/core/browser/page_usage_data.h"
 #include "components/history/core/browser/typed_url_syncable_service.h"
 #include "components/history/core/browser/url_utils.h"
-#include "components/memory_coordinator/browser/memory_coordinator.h"
 #include "net/base/registry_controlled_domains/registry_controlled_domain.h"
 #include "sql/error_delegate_util.h"
 #include "third_party/skia/include/core/SkBitmap.h"
@@ -235,11 +234,6 @@ HistoryBackend::~HistoryBackend() {
         FROM_HERE, backend_destroy_task_);
   }
 
-  if (memory_coordinator::MemoryCoordinator::GetInstance()) {
-    memory_coordinator::MemoryCoordinator::GetInstance()->UnregisterClient(
-        this);
-  }
-
 #if defined(OS_ANDROID)
   if (backend_client_ && !history_dir_.empty())
     backend_client_->OnHistoryBackendDestroyed(this, history_dir_);
@@ -258,12 +252,8 @@ void HistoryBackend::Init(
     InitImpl(history_database_params);
   delegate_->DBLoaded();
   typed_url_syncable_service_.reset(new TypedUrlSyncableService(this));
-  if (memory_coordinator::MemoryCoordinator::GetInstance()) {
-    memory_coordinator::MemoryCoordinator::GetInstance()->RegisterClient(this);
-  } else {
-    memory_pressure_listener_.reset(new base::MemoryPressureListener(
-        base::Bind(&HistoryBackend::OnMemoryPressure, base::Unretained(this))));
-  }
+  memory_pressure_listener_.reset(new base::MemoryPressureListener(
+      base::Bind(&HistoryBackend::OnMemoryPressure, base::Unretained(this))));
 }
 
 void HistoryBackend::SetOnBackendDestroyTask(base::MessageLoop* message_loop,
@@ -919,12 +909,6 @@ bool HistoryBackend::IsExpiredVisitTime(const base::Time& time) {
   return time < expirer_.GetCurrentExpirationTime();
 }
 
-void HistoryBackend::OnMemoryStateChange(
-    memory_coordinator::MemoryState state) {
-  bool trim_aggressively = state == memory_coordinator::MemoryState::SUSPENDED;
-  TrimMemory(trim_aggressively);
-}
-
 void HistoryBackend::SetPageTitle(const GURL& url,
                                   const base::string16& title) {
   if (!db_)