[tracing] Track number of allocations in heap profiler

base/trace_event/malloc_dump_provider.cc

Index: base/trace_event/malloc_dump_provider.cc
diff --git a/base/trace_event/malloc_dump_provider.cc b/base/trace_event/malloc_dump_provider.cc
index 17e5c1e62074f95720442ee3b49a944607b490bf..54322b7f616c5b4a270325b0739a550032846cea 100644
--- a/base/trace_event/malloc_dump_provider.cc
+++ b/base/trace_event/malloc_dump_provider.cc
@@ -178,21 +178,23 @@ bool MallocDumpProvider::OnMemoryDump(const MemoryDumpArgs& args,
   // profiler does not see unabalanced malloc/free calls from these containers.
   {
     TraceEventMemoryOverhead overhead;
-    hash_map<AllocationContext, size_t> bytes_by_context;
+    hash_map<AllocationContext, AllocationsSizeAndCount> metrics_by_context;
     {
       AutoLock lock(allocation_register_lock_);
       if (allocation_register_) {
         if (args.level_of_detail == MemoryDumpLevelOfDetail::DETAILED) {
-          for (const auto& alloc_size : *allocation_register_)
-            bytes_by_context[alloc_size.context] += alloc_size.size;
+          for (const auto& alloc_size : *allocation_register_) {
+            metrics_by_context[alloc_size.context].size += alloc_size.size;
+            metrics_by_context[alloc_size.context].count++;

[Dmitry Skiba, 2016/04/14 19:07:30]

Let's avoid second lookup by caching result from the first one.

[Primiano Tucci (use gerrit), 2016/04/14 19:37:21]

+1. Good suggestion ;-)

[ssid, 2016/04/14 20:17:10]

Done.

+          }
         }
         allocation_register_->EstimateTraceMemoryOverhead(&overhead);
       }
     }  // lock(allocation_register_lock_)
 
-    if (!bytes_by_context.empty()) {
+    if (!metrics_by_context.empty()) {
       std::unique_ptr<TracedValue> heap_dump = ExportHeapDump(
-          bytes_by_context, pmd->session_state()->stack_frame_deduplicator(),
+          metrics_by_context, pmd->session_state()->stack_frame_deduplicator(),
           pmd->session_state()->type_name_deduplicator());
       pmd->AddHeapDump("malloc", std::move(heap_dump));
     }