Change initialization strategy of AllocationRegister back

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 b96fdb7ce7abd6ab2f7fa7d1838a65f20caae817..5025908fc1ca84dd7f6aa366b6df08063a82f0b5 100644
--- a/third_party/WebKit/Source/platform/PartitionAllocMemoryDumpProvider.cpp
+++ b/third_party/WebKit/Source/platform/PartitionAllocMemoryDumpProvider.cpp
@@ -137,8 +137,9 @@ bool PartitionAllocMemoryDumpProvider::onMemoryDump(WebMemoryDumpLevelOfDetail l
     return true;
 }
 
+// |m_allocationRegister| should be initialized only when necessary to avoid waste of memory.
 PartitionAllocMemoryDumpProvider::PartitionAllocMemoryDumpProvider()
-    : m_allocationRegister(adoptPtr(new base::trace_event::AllocationRegister()))
+    : m_allocationRegister(nullptr)
     , m_isHeapProfilingEnabled(false)
 {
 }
@@ -150,6 +151,11 @@ PartitionAllocMemoryDumpProvider::~PartitionAllocMemoryDumpProvider()
 void PartitionAllocMemoryDumpProvider::onHeapProfilingEnabled(bool enabled)
 {
     if (enabled) {
+        {
+            MutexLocker locker(m_allocationRegisterMutex);
+            if (!m_allocationRegister)
+                m_allocationRegister = adoptPtr(new base::trace_event::AllocationRegister());
+        }
         PartitionAllocHooks::setAllocationHook(reportAllocation);
         PartitionAllocHooks::setFreeHook(reportFree);
     } else {
@@ -164,13 +170,15 @@ void PartitionAllocMemoryDumpProvider::insert(void* address, size_t size, const
     base::trace_event::AllocationContext context = base::trace_event::AllocationContextTracker::GetContextSnapshot();
     context.type_name = typeName;
     MutexLocker locker(m_allocationRegisterMutex);

[haraken, 2016/02/05 11:20:59]

Nit: It would be heavy to use MutexLocker in insert/remove. You could use
releaseStore/acquireLoad. You don't need to address it in this CL.

[Primiano Tucci (use gerrit), 2016/02/05 11:42:08]

Note that here we have also to protect against concurrent accesses to the
allocation register (Which is not thread safe)
is releaseStore/acquireLoad going to protect this?

-    m_allocationRegister->Insert(address, size, context);
+    if (m_allocationRegister)
+        m_allocationRegister->Insert(address, size, context);
 }
 
 void PartitionAllocMemoryDumpProvider::remove(void* address)
 {
     MutexLocker locker(m_allocationRegisterMutex);
-    m_allocationRegister->Remove(address);
+    if (m_allocationRegister)
+        m_allocationRegister->Remove(address);
 }
 
 } // namespace blink