[tracing] Add light dumps in the V8 dump provider

gin/v8_isolate_memory_dump_provider.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 "gin/v8_isolate_memory_dump_provider.h"
 
 #include "base/strings/stringprintf.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/trace_event/memory_dump_manager.h"
 #include "base/trace_event/process_memory_dump.h"
@@ skipping 17 matching lines @@
 // Called at trace dump point time. Creates a snapshot with the memory counters
 // for the current isolate.
 bool V8IsolateMemoryDumpProvider::OnMemoryDump(
     const base::trace_event::MemoryDumpArgs& args,
     base::trace_event::ProcessMemoryDump* process_memory_dump) {
   // TODO(ssid): Use MemoryDumpArgs to create light dumps when requested
   // (crbug.com/499731).
 
   if (isolate_holder_->access_mode() == IsolateHolder::kUseLocker) {
     v8::Locker locked(isolate_holder_->isolate());
-    DumpHeapStatistics(process_memory_dump);
+    DumpHeapStatistics(args, process_memory_dump);
   } else {
-    DumpHeapStatistics(process_memory_dump);
+    DumpHeapStatistics(args, process_memory_dump);
   }
   return true;
 }
 
 void V8IsolateMemoryDumpProvider::DumpHeapStatistics(
+    const base::trace_event::MemoryDumpArgs& args,
     base::trace_event::ProcessMemoryDump* process_memory_dump) {
   std::string dump_base_name =
       base::StringPrintf("v8/isolate_%p", isolate_holder_->isolate());
 
   // Dump statistics of the heap's spaces.
   std::string space_name_prefix = dump_base_name + "/heap_spaces";
   v8::HeapStatistics heap_statistics;
   isolate_holder_->isolate()->GetHeapStatistics(&heap_statistics);
 
   size_t known_spaces_used_size = 0;
@@ skipping 30 matching lines @@
                         base::trace_event::MemoryAllocatorDump::kUnitsBytes,
                         heap_statistics.total_heap_size() - known_spaces_size);
 
   auto other_allocated_dump = process_memory_dump->CreateAllocatorDump(
       other_spaces_name + "/allocated_objects");
   other_allocated_dump->AddScalar(
       base::trace_event::MemoryAllocatorDump::kNameSize,
       base::trace_event::MemoryAllocatorDump::kUnitsBytes,
       heap_statistics.used_heap_size() - known_spaces_used_size);
 
+  // If light dump is requested, then object statistics are not dumped
+  if (args.level_of_detail ==
+      base::trace_event::MemoryDumpArgs::LevelOfDetail::LOW)
+    return;
+
   // Dump statistics of the heap's live objects from last GC.
   std::string object_name_prefix = dump_base_name + "/heap_objects";
   bool did_dump_object_stats = false;
   const size_t object_types =
       isolate_holder_->isolate()->NumberOfTrackedHeapObjectTypes();
   for (size_t type_index = 0; type_index < object_types; type_index++) {
     v8::HeapObjectStatistics object_statistics;
     if (!isolate_holder_->isolate()->GetHeapObjectStatisticsAtLastGC(
             &object_statistics, type_index))
       continue;
@@ skipping 25 matching lines @@
   }
 
   if (did_dump_object_stats) {
     process_memory_dump->AddOwnershipEdge(
         process_memory_dump->CreateAllocatorDump(object_name_prefix)->guid(),
         process_memory_dump->CreateAllocatorDump(space_name_prefix)->guid());
   }
 }
 
 }  // namespace gin