Add support to create memory allocator dump in base::DiscardableMemory

content/common/host_discardable_shared_memory_manager.cc

 // Copyright 2014 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 "content/common/host_discardable_shared_memory_manager.h"
 
 #include <algorithm>
 
 #include "base/atomic_sequence_num.h"
 #include "base/bind.h"
@@ skipping 46 matching lines @@
     DCHECK(is_locked_);
 
     shared_memory_->Unlock(0, 0);
     is_locked_ = false;
   }
   void* data() const override {
     DCHECK(is_locked_);
     return shared_memory_->memory();
   }
 
+  base::trace_event::MemoryAllocatorDump* CreateMemoryAllocatorDump(
+      const char* name,
+      base::trace_event::ProcessMemoryDump* pmd) override {
+    // The memory could have been purged, but we still create a dump with
+    // mapped_size. So, the size can be inaccurate.
+    base::trace_event::MemoryAllocatorDump* dump =
+        pmd->CreateAllocatorDump(name);
+    dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                    base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                    shared_memory_->mapped_size());
+    return dump;
+  }
+
  private:
   scoped_ptr<base::DiscardableSharedMemory> shared_memory_;
+  size_t size_;

[reveman, 2015/08/24 16:50:06]

is this needed?

   const base::Closure deleted_callback_;
   bool is_locked_;
 
   DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryImpl);
 };
 
 base::LazyInstance<HostDiscardableSharedMemoryManager>
     g_discardable_shared_memory_manager = LAZY_INSTANCE_INITIALIZER;
 
 #if defined(OS_ANDROID)
@@ skipping 377 matching lines @@
 
   enforce_memory_policy_pending_ = true;
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE,
       base::Bind(&HostDiscardableSharedMemoryManager::EnforceMemoryPolicy,
                  weak_ptr_factory_.GetWeakPtr()),
       base::TimeDelta::FromMilliseconds(kEnforceMemoryPolicyDelayMs));
 }
 
 }  // namespace content