[Tentaive patch for discussion] Add Purge+Suspend metrics as UMA.

content/child/child_discardable_shared_memory_manager.h

 // 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.
 
 #ifndef CONTENT_CHILD_CHILD_DISCARDABLE_SHARED_MEMORY_MANAGER_H_
 #define CONTENT_CHILD_CHILD_DISCARDABLE_SHARED_MEMORY_MANAGER_H_
 
 #include <stddef.h>
 
 #include "base/macros.h"
@@ skipping 18 matching lines @@
   ~ChildDiscardableSharedMemoryManager() override;
 
   // Overridden from base::DiscardableMemoryAllocator:
   std::unique_ptr<base::DiscardableMemory> AllocateLockedDiscardableMemory(
       size_t size) override;
 
   // Overridden from base::trace_event::MemoryDumpProvider:
   bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
                     base::trace_event::ProcessMemoryDump* pmd) override;
 
+  size_t GetMemoryUsage() const;
+
   // Release memory and associated resources that have been purged.
   void ReleaseFreeMemory();
 
   bool LockSpan(DiscardableSharedMemoryHeap::Span* span);
   void UnlockSpan(DiscardableSharedMemoryHeap::Span* span);
   void ReleaseSpan(std::unique_ptr<DiscardableSharedMemoryHeap::Span> span);
 
   base::trace_event::MemoryAllocatorDump* CreateMemoryAllocatorDump(
       DiscardableSharedMemoryHeap::Span* span,
       const char* name,
       base::trace_event::ProcessMemoryDump* pmd) const;
 
  private:
   std::unique_ptr<base::DiscardableSharedMemory>
   AllocateLockedDiscardableSharedMemory(size_t size,
                                         DiscardableSharedMemoryId id);
   void MemoryUsageChanged(size_t new_bytes_allocated,
                           size_t new_bytes_free) const;
 
   mutable base::Lock lock_;
   DiscardableSharedMemoryHeap heap_;
   scoped_refptr<ThreadSafeSender> sender_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildDiscardableSharedMemoryManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_CHILD_DISCARDABLE_SHARED_MEMORY_MANAGER_H_