[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..c028773303e3da43dadd4d754c0f681b47103e67 100644
--- a/third_party/WebKit/Source/wtf/PartitionAlloc.h
+++ b/third_party/WebKit/Source/wtf/PartitionAlloc.h
@@ -411,6 +411,9 @@ 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*);
 
+extern WTF_EXPORT void (*partitionAllocHookAlloc)(void* addr, size_t size);

[Primiano Tucci (use gerrit), 2015/10/12 16:36:46]

Hmm I think that if you split this into the actual fptr declaration and the
storage definition it will be more clear and will reduce code duplication w.r.t.
the .cc file
also making them static fields of some class would remove the need of the
awkward "extern"

[Ruud van Asseldonk, 2015/10/13 10:42:18]

Done.

+extern WTF_EXPORT void (*partitionAllocHookFree)(void* addr);
+
 ALWAYS_INLINE PartitionFreelistEntry* partitionFreelistMask(PartitionFreelistEntry* ptr)
 {
     // We use bswap on little endian as a fast mask for two reasons:
@@ -701,6 +704,10 @@ ALWAYS_INLINE void* partitionAllocGenericFlags(PartitionRootGeneric* root, int f
     spinLockLock(&root->lock);
     void* ret = partitionBucketAlloc(root, flags, size, bucket);
     spinLockUnlock(&root->lock);
+
+    if (UNLIKELY(partitionAllocHookAlloc != nullptr))

[Primiano Tucci (use gerrit), 2015/10/12 16:36:46]

see my previous comment about locking. I think you might want to move this under
the spinlock.

[Primiano Tucci (use gerrit), 2015/10/12 16:36:46]

Also, if you hook only partitionAllocGeneric you will miss the calls entering
via partitionAlloc() and partitionFree() 

[Ruud van Asseldonk, 2015/10/13 10:42:18]

Oooops, should have hooked |partitionBucketAlloc| and |partitionFreeWithPage| in
the common code path.

+        partitionAllocHookAlloc(ret, size);
+
     return ret;
 #endif
 }
@@ -717,6 +724,9 @@ ALWAYS_INLINE void partitionFreeGeneric(PartitionRootGeneric* root, void* ptr)
 #else
     ASSERT(root->initialized);
 
+    if (UNLIKELY(partitionAllocHookFree != nullptr))

[Primiano Tucci (use gerrit), 2015/10/12 16:36:46]

ditto

[Ruud van Asseldonk, 2015/10/13 10:42:18]

Yes.

+        partitionAllocHookFree(ptr);
+
     if (UNLIKELY(!ptr))
         return;