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

content/common/host_discardable_shared_memory_manager.cc

Index: content/common/host_discardable_shared_memory_manager.cc
diff --git a/content/common/host_discardable_shared_memory_manager.cc b/content/common/host_discardable_shared_memory_manager.cc
index 7590c1f9bb4c6848f950a21da491494ab04ea0d8..23b1601c772fea2c2adadb7869ee5d93f559adc9 100644
--- a/content/common/host_discardable_shared_memory_manager.cc
+++ b/content/common/host_discardable_shared_memory_manager.cc
@@ -31,8 +31,10 @@ namespace {
 class DiscardableMemoryImpl : public base::DiscardableMemory {
  public:
   DiscardableMemoryImpl(scoped_ptr<base::DiscardableSharedMemory> shared_memory,
+                        size_t size,

[reveman, 2015/08/21 18:05:24]

can we use shared_memory->mapped_size() instead?

[ssid, 2015/08/24 14:52:10]

Done.

                         const base::Closure& deleted_callback)
       : shared_memory_(shared_memory.Pass()),
+        size_(size),
         deleted_callback_(deleted_callback),
         is_locked_(true) {}
 
@@ -64,8 +66,21 @@ class DiscardableMemoryImpl : public base::DiscardableMemory {
     return shared_memory_->memory();
   }
 
+  base::trace_event::MemoryAllocatorDump* CreateMemoryAllocatorDump(
+      const char* name,
+      base::trace_event::ProcessMemoryDump* pmd) override {
+    // The memory could have been purged by the heap, but we still create a

[reveman, 2015/08/21 18:05:24]

note: there's no heap in this case

[ssid, 2015/08/24 14:52:10]

Done.

+    // dump. 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, size_);
+    return dump;
+  }
+
  private:
   scoped_ptr<base::DiscardableSharedMemory> shared_memory_;
+  size_t size_;
   const base::Closure deleted_callback_;
   bool is_locked_;
 
@@ -147,7 +162,7 @@ HostDiscardableSharedMemoryManager::AllocateLockedDiscardableMemory(
   // Close file descriptor to avoid running out.
   memory->Close();
   return make_scoped_ptr(new DiscardableMemoryImpl(
-      memory.Pass(),
+      memory.Pass(), size,
       base::Bind(
           &HostDiscardableSharedMemoryManager::DeletedDiscardableSharedMemory,
           base::Unretained(this), new_id, ChildProcessHost::kInvalidUniqueID)));