[tracing] Display the locked size of discardable memory segment.

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 162 matching lines @@
   for (const auto& process_entry : processes_) {
     const int child_process_id = process_entry.first;
     const MemorySegmentMap& process_segments = process_entry.second;
     for (const auto& segment_entry : process_segments) {
       const int segment_id = segment_entry.first;
       const MemorySegment* segment = segment_entry.second.get();
       std::string dump_name = base::StringPrintf(
           "discardable/process_%x/segment_%d", child_process_id, segment_id);
       base::trace_event::MemoryAllocatorDump* dump =
           pmd->CreateAllocatorDump(dump_name);
+
+      const size_t mapped_size = segment->memory()->mapped_size();

[reveman, 2015/10/01 10:34:40]

fyi: mapped_size() being lower case means it's a cheap getter so you can avoid
this temporary variable if you like

[ssid, 2015/10/01 14:08:46]

Added only because of the line sizes. don't really have an opinion

       dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
                       base::trace_event::MemoryAllocatorDump::kUnitsBytes,
-                      segment->memory()->mapped_size());
+                      mapped_size);
+
+      // Host can only tell if whole segment is locked or not.
+      dump->AddScalar("locked_size",
+                      base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                      segment->memory()->IsMemoryLocked() ? mapped_size : 0u);
 
       // Create the cross-process ownership edge. If the child creates a
       // corresponding dump for the same segment, this will avoid to
       // double-count them in tracing. If, instead, no other process will emit a
       // dump with the same guid, the segment will be accounted to the browser.
       const uint64 child_tracing_process_id =
           ChildProcessHostImpl::ChildProcessUniqueIdToTracingProcessId(
               child_process_id);
       base::trace_event::MemoryAllocatorDumpGuid shared_segment_guid =
           DiscardableSharedMemoryHeap::GetSegmentGUIDForTracing(
@@ skipping 270 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