Use DiscardableMemoryManager on Android.

base/memory/discardable_memory.h

 // Copyright (c) 2013 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.
 
 #ifndef BASE_MEMORY_DISCARDABLE_MEMORY_H_
 #define BASE_MEMORY_DISCARDABLE_MEMORY_H_
 
 #include <string>
 #include <vector>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
 
 enum DiscardableMemoryType {
   DISCARDABLE_MEMORY_TYPE_NONE,
-  DISCARDABLE_MEMORY_TYPE_ANDROID,
+  DISCARDABLE_MEMORY_TYPE_ASHMEM,
   DISCARDABLE_MEMORY_TYPE_MAC,
   DISCARDABLE_MEMORY_TYPE_EMULATED,
   DISCARDABLE_MEMORY_TYPE_MALLOC
 };
 
 enum DiscardableMemoryLockStatus {
   DISCARDABLE_MEMORY_LOCK_STATUS_FAILED,
   DISCARDABLE_MEMORY_LOCK_STATUS_PURGED,
   DISCARDABLE_MEMORY_LOCK_STATUS_SUCCESS
 };
@@ skipping 79 matching lines @@
   virtual void Unlock() = 0;
 
   // Returns the memory address held by this object. The object must be locked
   // before calling this. Otherwise, this will cause a DCHECK error.
   virtual void* Memory() const = 0;
 
   // Testing utility calls.
 
   // Check whether a purge of all discardable memory in the system is supported.
   // Use only for testing!
-  static bool PurgeForTestingSupported();
+  static bool PurgeForTestingSupported(DiscardableMemoryType type);

[reveman, 2014/04/28 15:39:16]

How about we just remove PurgeForTestingSupported now that it's supported by all
types?

[Philippe, 2014/04/28 15:53:45]

I would be happy to do that but unfortunately the malloc type doesn't support
purging. I wasn't very comfortable with adding some extra global state keeping
track of the allocations just for testing but I can reconsider that. 

[reveman, 2014/04/28 16:02:24]

I think purging in the case of the malloc type is a NoOp. Everything that can be
purged is already purged.

 
   // Purge all discardable memory in the system. This call has global effects
   // across all running processes, so it should only be used for testing!
-  static void PurgeForTesting();
+  static void PurgeForTesting(DiscardableMemoryType type);

[reveman, 2014/04/28 15:39:16]

Can you explain why we need to pass a type here instead of just purging memory
for all supported types?

[Philippe, 2014/04/28 15:53:45]

Just to clarify, I was initially overriding the preferred type in the test
fixture and having PurgeForTesting() rely on the current global preferred type
but I was hitting a DCHECK() (which is quite valuable IMO) asserting that we are
setting the preferred type only once. So I thought it would be easier to avoid
messing up with the global state.

Does that make sense?

[reveman, 2014/04/28 16:02:24]

I agree that we shouldn't mess with preferred type here. It's just not clear to
me why PurgeForTesting can't look like this on Android:

PurgeForTesting {
  g_context.Pointer()->manager.PurgeAll();
  internal::DiscardableMemoryEmulated::PurgeForTesting();
}

[Philippe, 2014/04/28 16:31:21]

Yeah, good idea. I got rid of PurgeForTestingSupported().

 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_DISCARDABLE_MEMORY_H_