Purge browser cache for dom storage in a smarter way

content/browser/dom_storage/dom_storage_context_impl.h

Index: content/browser/dom_storage/dom_storage_context_impl.h
diff --git a/content/browser/dom_storage/dom_storage_context_impl.h b/content/browser/dom_storage/dom_storage_context_impl.h
index c2bbe4d42b50fcd2991e976540e64a6e1b58acc0..ad8e5d71adebb370b65dc08fcb1944ede8805dcb 100644
--- a/content/browser/dom_storage/dom_storage_context_impl.h
+++ b/content/browser/dom_storage/dom_storage_context_impl.h
@@ -15,6 +15,7 @@
 #include "base/atomic_sequence_num.h"
 #include "base/files/file_path.h"
 #include "base/gtest_prod_util.h"
+#include "base/memory/memory_pressure_listener.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
 #include "base/time/time.h"
@@ -175,11 +176,16 @@ class CONTENT_EXPORT DOMStorageContextImpl
   // unclean exit.
   void StartScavengingUnusedSessionStorage();
 
+  // Called on the |task_runner| to purge memory in case of memory pressure.
+  void PurgeMemory(
+      base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
+
   // base::trace_event::MemoryDumpProvider implementation.
   bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
                     base::trace_event::ProcessMemoryDump* pmd) override;
 
  private:
+  class DOMStorageMemoryPressureListener;
   friend class DOMStorageContextImplTest;
   FRIEND_TEST_ALL_PREFIXES(DOMStorageContextImplTest, Basics);
   friend class base::RefCountedThreadSafe<DOMStorageContextImpl>;
@@ -238,6 +244,9 @@ class CONTENT_EXPORT DOMStorageContextImpl
   // Mapping between persistent namespace IDs and namespace IDs for
   // sessionStorage.
   std::map<std::string, int64_t> persistent_namespace_id_to_namespace_id_;
+
+  // Notifier for memory pressure signals to purges memory.
+  DOMStorageMemoryPressureListener* leaked_memory_pressure_listener_;
 };
 
 }  // namespace content