Also report peak malloc memory usage from V8

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 <inttypes.h>
 #include <stddef.h>
 
 #include "base/strings/stringprintf.h"
@@ skipping 154 matching lines @@
                          base::trace_event::MemoryAllocatorDump::kUnitsBytes,
                          heap_statistics.malloced_memory());
   const char* system_allocator_name =
       base::trace_event::MemoryDumpManager::GetInstance()
           ->system_allocator_pool_name();
   if (system_allocator_name) {
     process_memory_dump->AddSuballocation(malloc_dump->guid(),
                                           system_allocator_name);
   }
 
+  std::string peak_malloc_name = dump_base_name + "/malloc_peak";

[primiano CORP (USE chromium), 2016/07/18 10:58:00]

I think the best approach would be reporting this as a column not a row,
otherwise would create funky double-counting issues, where we count both the
current and peak value.
Concretely this means turning this CL into a one-line (% wrapping) as follows:

malloc_dump->AddScalar("peak_size",
base::trace_event::MemoryAllocatorDump::kUnitsBytes,
heap_statistics.peak_malloced_memory())

+  auto* peak_malloc_dump =
+      process_memory_dump->CreateAllocatorDump(peak_malloc_name);
+  peak_malloc_dump->AddScalar(
+      base::trace_event::MemoryAllocatorDump::kNameSize,
+      base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+      heap_statistics.peak_malloced_memory());
+
   // Add an empty row for the heap_spaces. This is to keep the shape of the
   // dump stable, whether code stats are enabled or not.
   auto* heap_spaces_dump =
       process_memory_dump->CreateAllocatorDump(space_name_prefix);
 
   // Dump object statistics only for detailed dumps.
   if (args.level_of_detail !=
       base::trace_event::MemoryDumpLevelOfDetail::DETAILED) {
     return;
   }
@@ skipping 41 matching lines @@
     process_memory_dump->AddOwnershipEdge(
         process_memory_dump->CreateAllocatorDump(object_name_prefix)->guid(),
         heap_spaces_dump->guid());
   }
 
   // Dump statistics related to code and bytecode if requested.
   DumpCodeStatistics(heap_spaces_dump, isolate_holder_);
 }
 
 }  // namespace gin