Make SSLClientSessionCache a client of memory coordinator

When the memory coordinator is enabled, SSLClientSessionCache becomes a
client of the memory coordinator instead of installing
MemoryPressureListener.

In the implmentation of this CL, both MemoryPressureListener and
MemoryCoordinatorClient are installed regardless of the flag, but as
default MemoryCoordinator is not enabled and when MemoryCoordinator is
enabled by a flag, it is planed to suppress MemoryPressureMonitor
features.

Design Doc: https://docs.google.com/document/d/1a69mMr7jI7qK0OfKNlrZ350xiXizVMCCe8orGX7K8Uo/edit?ts=57d7968b#

BUG=639700

Review-Url: https://codereview.chromium.org/2384703002
Cr-Commit-Position: refs/heads/master@{#422697}

net/ssl/ssl_client_session_cache.cc

@@ -6,6 +6,7 @@
 
 #include <utility>
 
+#include "base/memory/memory_coordinator_client_registry.h"
 #include "base/time/clock.h"
 #include "base/time/default_clock.h"
 
@@ -18,10 +19,12 @@ SSLClientSessionCache::SSLClientSessionCache(const Config& config)
       lookups_since_flush_(0) {
   memory_pressure_listener_.reset(new base::MemoryPressureListener(base::Bind(
       &SSLClientSessionCache::OnMemoryPressure, base::Unretained(this))));
+  base::MemoryCoordinatorClientRegistry::GetInstance()->Register(this);
 }
 
 SSLClientSessionCache::~SSLClientSessionCache() {
   Flush();
+  base::MemoryCoordinatorClientRegistry::GetInstance()->Unregister(this);
 }
 
 size_t SSLClientSessionCache::size() const {
@@ -112,4 +115,22 @@ void SSLClientSessionCache::OnMemoryPressure(
   }
 }
 
+void SSLClientSessionCache::OnMemoryStateChange(base::MemoryState state) {
+  // TODO(hajimehoshi): When the state changes, adjust the sizes of the caches
+  // to reduce the limits. SSLClientSessionCache doesn't have the ability to
+  // limit at present.
+  switch (state) {
+    case base::MemoryState::NORMAL:
+      break;
+    case base::MemoryState::THROTTLED:
+      Flush();
+      break;
+    case base::MemoryState::SUSPENDED:
+    // Note: Not supported at present. Fall through.
+    case base::MemoryState::UNKNOWN:
+      NOTREACHED();
+      break;
+  }
+}
+
 }  // namespace net

net/ssl/ssl_client_session_cache.h

@@ -14,6 +14,7 @@
 #include "base/bind.h"
 #include "base/containers/mru_cache.h"
 #include "base/macros.h"
+#include "base/memory/memory_coordinator_client.h"
 #include "base/memory/memory_pressure_monitor.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/thread_checker.h"
@@ -27,7 +28,7 @@ class Clock;
 
 namespace net {
 
-class NET_EXPORT SSLClientSessionCache {
+class NET_EXPORT SSLClientSessionCache : public base::MemoryCoordinatorClient {
  public:
   struct Config {
     // The maximum number of entries in the cache.
@@ -39,7 +40,7 @@ class NET_EXPORT SSLClientSessionCache {
   };
 
   explicit SSLClientSessionCache(const Config& config);
-  ~SSLClientSessionCache();
+  ~SSLClientSessionCache() override;
 
   size_t size() const;
 
@@ -70,6 +71,9 @@ class NET_EXPORT SSLClientSessionCache {
   using CacheEntryMap =
       base::HashingMRUCache<std::string, std::unique_ptr<CacheEntry>>;
 
+  // base::MemoryCoordinatorClient implementation:
+  void OnMemoryStateChange(base::MemoryState state) override;
+
   // Returns true if |entry| is expired as of |now|.
   bool IsExpired(CacheEntry* entry, const base::Time& now);