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 ff46dd8c34b1032a78050d742cfe70eacf79389e..d92049f71f0fd19e42b304c6586d0cde80fb4702 100644
--- a/components/history/core/browser/history_backend.cc
+++ b/components/history/core/browser/history_backend.cc
@@ -41,7 +41,6 @@
 #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"
@@ -237,11 +236,6 @@ 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_);
@@ -260,12 +254,8 @@ 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,
@@ -749,19 +739,15 @@ void HistoryBackend::InitImpl(
   LOCAL_HISTOGRAM_TIMES("History.InitTime", TimeTicks::Now() - beginning_time);
 }
 
-void HistoryBackend::TrimMemory(bool trim_aggressively) {
-  if (db_)
-    db_->TrimMemory(trim_aggressively);
-  if (thumbnail_db_)
-    thumbnail_db_->TrimMemory(trim_aggressively);
-}
-
 void HistoryBackend::OnMemoryPressure(
     base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level) {
   bool trim_aggressively =
       memory_pressure_level ==
       base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL;
-  TrimMemory(trim_aggressively);
+  if (db_)
+    db_->TrimMemory(trim_aggressively);
+  if (thumbnail_db_)
+    thumbnail_db_->TrimMemory(trim_aggressively);
 }
 
 void HistoryBackend::CloseAllDatabases() {
@@ -921,12 +907,6 @@ 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_)