[tracing] Only add totals from discardable memory in background mode

content/child/child_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/child/child_discardable_shared_memory_manager.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/atomic_sequence_num.h"
@@ skipping 196 matching lines @@
 
   MemoryUsageChanged(heap_.GetSize(), heap_.GetSizeOfFreeLists());
 
   return base::WrapUnique(new DiscardableMemoryImpl(this, std::move(new_span)));
 }
 
 bool ChildDiscardableSharedMemoryManager::OnMemoryDump(
     const base::trace_event::MemoryDumpArgs& args,
     base::trace_event::ProcessMemoryDump* pmd) {
   base::AutoLock lock(lock_);
+  if (args.level_of_detail ==
+      base::trace_event::MemoryDumpLevelOfDetail::BACKGROUND) {
+    base::trace_event::MemoryAllocatorDump* total_dump =
+        pmd->CreateAllocatorDump("discardable");
+    const size_t total_size = heap_.GetSize();
+    const size_t freelist_size = heap_.GetSizeOfFreeLists();
+    total_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                          base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                          total_size - freelist_size);
+    total_dump->AddScalar("freelist_size",
+                          base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                          freelist_size);
+    return true;
+  }
+
   return heap_.OnMemoryDump(pmd);
 }
 
 void ChildDiscardableSharedMemoryManager::ReleaseFreeMemory() {
   base::AutoLock lock(lock_);
 
   size_t heap_size_prior_to_releasing_memory = heap_.GetSize();
 
   // Release both purged and free memory.
   heap_.ReleasePurgedMemory();
@@ skipping 93 matching lines @@
       "discardable-memory-allocated";
   base::debug::SetCrashKeyValue(kDiscardableMemoryAllocatedKey,
                                 base::Uint64ToString(new_bytes_total));
 
   static const char kDiscardableMemoryFreeKey[] = "discardable-memory-free";
   base::debug::SetCrashKeyValue(kDiscardableMemoryFreeKey,
                                 base::Uint64ToString(new_bytes_free));
 }
 
 }  // namespace content