blink MemoryCoordinator::onPurgeMemory should invoke each client's onPurgeMemory.

third_party/WebKit/Source/platform/MemoryCoordinator.cpp

 // Copyright 2015 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 "platform/MemoryCoordinator.h"
 
 #include "base/sys_info.h"
 #include "platform/fonts/FontCache.h"
 #include "platform/graphics/ImageDecodingStore.h"
 #include "platform/instrumentation/tracing/TraceEvent.h"
@@ skipping 50 matching lines @@
     clearMemory();
   WTF::Partitions::decommitFreeableMemory();
 }
 
 void MemoryCoordinator::onMemoryStateChange(MemoryState state) {
   for (auto& client : m_clients)
     client->onMemoryStateChange(state);
 }
 
 void MemoryCoordinator::onPurgeMemory() {
+  for (auto& client : m_clients)
+    client->onPurgeMemory();
   // Don't call clearMemory() because font cache invalidation always causes full
   // layout. This increases tab switching cost significantly (e.g.
   // en.wikipedia.org/wiki/Wikipedia). So we should not invalidate the font
   // cache in purge+throttle.
   ImageDecodingStore::instance().clear();
   WTF::Partitions::decommitFreeableMemory();
 }
 
 void MemoryCoordinator::clearMemory() {
   // Clear the image cache.
   // TODO(tasak|bashi): Make ImageDecodingStore and FontCache be
   // MemoryCoordinatorClients rather than clearing caches here.
   ImageDecodingStore::instance().clear();
   FontCache::fontCache()->invalidate();
 }
 
 DEFINE_TRACE(MemoryCoordinator) {
   visitor->trace(m_clients);
 }
 
 }  // namespace blink