[tracing] Add method to create "weak" global dumps

base/trace_event/process_memory_dump.cc

 // Copyright 2015 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 "base/trace_event/process_memory_dump.h"
 
 #include <errno.h>
 #include <vector>
 
 #include "base/process/process_metrics.h"
@@ skipping 117 matching lines @@
 MemoryAllocatorDump* ProcessMemoryDump::GetOrCreateAllocatorDump(
     const std::string& absolute_name) {
   MemoryAllocatorDump* mad = GetAllocatorDump(absolute_name);
   return mad ? mad : CreateAllocatorDump(absolute_name);
 }
 
 MemoryAllocatorDump* ProcessMemoryDump::CreateSharedGlobalAllocatorDump(
     const MemoryAllocatorDumpGuid& guid) {
   // A shared allocator dump can be shared within a process and the guid could
   // have been created already.
-  MemoryAllocatorDump* allocator_dump = GetSharedGlobalAllocatorDump(guid);
-  return allocator_dump ? allocator_dump
-                        : CreateAllocatorDump(
-                              GetSharedGlobalAllocatorDumpName(guid), guid);
+  MemoryAllocatorDump* mad = GetSharedGlobalAllocatorDump(guid);
+  if (mad) {
+    // The weak flag is cleared because this method should create a non-weak
+    // dump.
+    mad->clear_flags(MemoryAllocatorDump::Flags::WEAK);
+    return mad;
+  }
+  return CreateAllocatorDump(GetSharedGlobalAllocatorDumpName(guid), guid);
+}
+
+MemoryAllocatorDump* ProcessMemoryDump::CreateWeakSharedGlobalAllocatorDump(
+    const MemoryAllocatorDumpGuid& guid) {
+  MemoryAllocatorDump* mad = GetSharedGlobalAllocatorDump(guid);
+  if (mad)
+    return mad;
+  mad = CreateAllocatorDump(GetSharedGlobalAllocatorDumpName(guid), guid);
+  mad->set_flags(MemoryAllocatorDump::Flags::WEAK);
+  return mad;
 }
 
 MemoryAllocatorDump* ProcessMemoryDump::GetSharedGlobalAllocatorDump(
     const MemoryAllocatorDumpGuid& guid) const {
   return GetAllocatorDump(GetSharedGlobalAllocatorDumpName(guid));
 }
 
 void ProcessMemoryDump::AddHeapDump(const std::string& absolute_name,
                                     scoped_refptr<TracedValue> heap_dump) {
   DCHECK_EQ(0ul, heap_dumps_.count(absolute_name));
@@ skipping 95 matching lines @@
 
 void ProcessMemoryDump::AddSuballocation(const MemoryAllocatorDumpGuid& source,
                                          const std::string& target_node_name) {
   std::string child_mad_name = target_node_name + "/__" + source.ToString();
   MemoryAllocatorDump* target_child_mad = CreateAllocatorDump(child_mad_name);
   AddOwnershipEdge(source, target_child_mad->guid());
 }
 
 }  // namespace trace_event
 }  // namespace base