base: Discardable memory types.

base/memory/discardable_memory.h

Index: base/memory/discardable_memory.h
diff --git a/base/memory/discardable_memory.h b/base/memory/discardable_memory.h
index cbc2db630a86f6e5a7b5483723cd52f75fecf380..7ca5cb6e1e76a834ed512ee16a292df2a2e9696f 100644
--- a/base/memory/discardable_memory.h
+++ b/base/memory/discardable_memory.h
@@ -5,6 +5,8 @@
 #ifndef BASE_MEMORY_DISCARDABLE_MEMORY_H_
 #define BASE_MEMORY_DISCARDABLE_MEMORY_H_
 
+#include <vector>
+
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
@@ -12,6 +14,13 @@
 
 namespace base {
 
+enum DiscardableMemoryType {
+  DISCARDABLE_MEMORY_NONE,
+  DISCARDABLE_MEMORY_ANDROID,

[reveman, 2013/12/13 18:21:53]

Follow up patches will replace this with DISCARDABLE_MEMORY_ASHMEM, which will
be supported on both android and chromeos.

+  DISCARDABLE_MEMORY_MAC,

[reveman, 2013/12/13 18:21:53]

We might want to rename this to DISCARDABLE_MEMORY_VM or
DISCARDABLE_MEMORY_VM_PURGEABLE in a follow up patch and move the implementation
out of _mac.cc if we need some implementation specific unit tests.

+  DISCARDABLE_MEMORY_EMULATED
+};
+
 enum LockDiscardableMemoryStatus {

[reveman, 2013/12/16 21:05:51]

How about we rename this to DiscardableMemoryLockStatus and use
DISCARDABLE_MEMORY_LOCK_STATUS_ prefix for all values? The prefix for the type
values above would then become DISCARDABLE_MEMORY_TYPE_.

[Philippe, 2013/12/17 14:28:21]

SGTM

[reveman, 2013/12/18 08:12:38]

Done.

   DISCARDABLE_MEMORY_FAILED = -1,
   DISCARDABLE_MEMORY_PURGED = 0,
@@ -53,9 +62,15 @@ class BASE_EXPORT DiscardableMemory {
  public:
   virtual ~DiscardableMemory() {}
 
-  // Check whether the system supports discardable memory natively. Returns
-  // false if the support is emulated.
-  static bool SupportedNatively();
+  // Get system supported discardable memory types. Preferred type at the front
+  // of vector.
+  static const std::vector<DiscardableMemoryType>& GetSupportedTypes();
+
+  // Set the current discardable memory type.
+  static void SetType(DiscardableMemoryType type);
+
+  // Get the current discardable memory type.
+  static DiscardableMemoryType GetType();
 
   static scoped_ptr<DiscardableMemory> CreateLockedMemory(size_t size);