[Tracing] Add hook to PartitionAlloc for heap profiling

third_party/WebKit/Source/wtf/PartitionAlloc.h

Index: third_party/WebKit/Source/wtf/PartitionAlloc.h
diff --git a/third_party/WebKit/Source/wtf/PartitionAlloc.h b/third_party/WebKit/Source/wtf/PartitionAlloc.h
index b0e233f4e2d24a442be2936fc08401c1fddc2866..e2f90d12477056abbcd0349696d58cf46ace6ed7 100644
--- a/third_party/WebKit/Source/wtf/PartitionAlloc.h
+++ b/third_party/WebKit/Source/wtf/PartitionAlloc.h
@@ -411,6 +411,17 @@ WTF_EXPORT NEVER_INLINE void* partitionReallocGeneric(PartitionRootGeneric*, voi
 WTF_EXPORT void partitionDumpStats(PartitionRoot*, const char* partitionName, bool isLightDump, PartitionStatsDumper*);
 WTF_EXPORT void partitionDumpStatsGeneric(PartitionRootGeneric*, const char* partitionName, bool isLightDump, PartitionStatsDumper*);
 
+class WTF_EXPORT PartitionHooks {

[Primiano Tucci (use gerrit), 2015/10/14 10:10:12]

nit: PartitionAllocHooks ? otherwise it seems that you are hooking
partition-specific events

[Ruud van Asseldonk, 2015/10/14 12:30:18]

Done.

+public:
+    typedef void AllocationHook(void* address, size_t);
+    typedef void FreeHook(void* address);
+
+    // Pointers to hook functions that PartitionAlloc will call on allocation and
+    // free if the pointers are non-null.
+    static AllocationHook* allocationHook;

[Primiano Tucci (use gerrit), 2015/10/14 10:10:12]

nit: m_allocationHook i believe

[Ruud van Asseldonk, 2015/10/14 12:30:18]

Done.

+    static FreeHook* freeHook;

[Primiano Tucci (use gerrit), 2015/10/14 10:10:12]

I think you can make the static private: and expose inline public methods which
do the null-check (using local variables) + call.
This would reduce the boilerplate elsewhere, like

inline void maybeInvokeAllocationHook(void* address, size_t size) {
  AllocationHook* hook = m_allocationHook;
  if (hook)
   hook(address, size);
}

[Ruud van Asseldonk, 2015/10/14 12:30:18]

Great idea, done.

+};
+
 ALWAYS_INLINE PartitionFreelistEntry* partitionFreelistMask(PartitionFreelistEntry* ptr)
 {
     // We use bswap on little endian as a fast mask for two reasons:
@@ -613,6 +624,10 @@ ALWAYS_INLINE void* partitionBucketAlloc(PartitionRootBase* root, int flags, siz
     partitionCookieWriteValue(charRet);
     partitionCookieWriteValue(charRet + kCookieSize + noCookieSize);
 #endif
+
+    if (UNLIKELY(PartitionHooks::allocationHook != nullptr))
+        PartitionHooks::allocationHook(ret, size);
+
     return ret;
 }
 
@@ -645,6 +660,10 @@ ALWAYS_INLINE void partitionFreeWithPage(void* ptr, PartitionPage* page)
     partitionCookieCheckValue(reinterpret_cast<char*>(ptr) + slotSize - kCookieSize);
     memset(ptr, kFreedByte, slotSize);
 #endif
+
+    if (UNLIKELY(PartitionHooks::freeHook != nullptr))
+        PartitionHooks::freeHook(ptr);
+
     ASSERT(page->numAllocatedSlots);
     PartitionFreelistEntry* freelistHead = page->freelistHead;
     ASSERT(!freelistHead || partitionPointerIsValid(freelistHead));