[tracing] Track number of allocations in heap profiler

third_party/WebKit/Source/platform/PartitionAllocMemoryDumpProvider.cpp

Index: third_party/WebKit/Source/platform/PartitionAllocMemoryDumpProvider.cpp
diff --git a/third_party/WebKit/Source/platform/PartitionAllocMemoryDumpProvider.cpp b/third_party/WebKit/Source/platform/PartitionAllocMemoryDumpProvider.cpp
index d269b2935139513e1d1452d0d4f7d7aa39f788ba..fb2431939d1f530f1fd534d01f42569446ff3eb0 100644
--- a/third_party/WebKit/Source/platform/PartitionAllocMemoryDumpProvider.cpp
+++ b/third_party/WebKit/Source/platform/PartitionAllocMemoryDumpProvider.cpp
@@ -112,17 +112,19 @@ bool PartitionAllocMemoryDumpProvider::onMemoryDump(WebMemoryDumpLevelOfDetail l
     if (m_isHeapProfilingEnabled) {
         // Overhead should always be reported, regardless of light vs. heavy.
         base::trace_event::TraceEventMemoryOverhead overhead;
-        base::hash_map<base::trace_event::AllocationContext, size_t> bytesByContext;
+        base::hash_map<base::trace_event::AllocationContext, base::trace_event::AllocationsSizeAndCount> metricsByContext;

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

I wonder if we should have typedef for this, like AllocationMetricsByContext or
something, because every dump provider have to declare it.

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

IMHO typedef just make the code less readable as you have to clink another thing
to realize that this is a hashtable under the hoods.
I'll probably leave as it is, it's just 3 dump providers after all:)

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

Acknowledged.

         {
             MutexLocker locker(m_allocationRegisterMutex);
             // Dump only the overhead estimation in non-detailed dumps.
             if (levelOfDetail == WebMemoryDumpLevelOfDetail::Detailed) {
-                for (const auto& allocSize : *m_allocationRegister)
-                    bytesByContext[allocSize.context] += allocSize.size;
+                for (const auto& allocSize : *m_allocationRegister) {
+                    metricsByContext[allocSize.context].size += allocSize.size;
+                    metricsByContext[allocSize.context].count++;

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

Avoid second lookup.

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

Done.

+                }
             }
             m_allocationRegister->EstimateTraceMemoryOverhead(&overhead);
         }
-        memoryDump->dumpHeapUsage(bytesByContext, overhead, "partition_alloc");
+        memoryDump->dumpHeapUsage(metricsByContext, overhead, "partition_alloc");
     }
 
     PartitionStatsDumperImpl partitionStatsDumper(memoryDump, levelOfDetail);