[Tracing] Add hook to PartitionAlloc for heap profiling

third_party/WebKit/Source/wtf/PartitionAlloc.cpp

Index: third_party/WebKit/Source/wtf/PartitionAlloc.cpp
diff --git a/third_party/WebKit/Source/wtf/PartitionAlloc.cpp b/third_party/WebKit/Source/wtf/PartitionAlloc.cpp
index d076568fcfc59bd6984d319884c0c6c19b18d6af..7f474b4a523161a8c3a17d0e9bce54833b500cce 100644
--- a/third_party/WebKit/Source/wtf/PartitionAlloc.cpp
+++ b/third_party/WebKit/Source/wtf/PartitionAlloc.cpp
@@ -60,6 +60,8 @@ bool PartitionRootBase::gInitialized = false;
 PartitionPage PartitionRootBase::gSeedPage;
 PartitionBucket PartitionRootBase::gPagedBucket;
 void (*PartitionRootBase::gOomHandlingFunction)() = nullptr;
+PartitionHooks::AllocationHook* PartitionHooks::allocationHook = nullptr;
+PartitionHooks::FreeHook* PartitionHooks::freeHook = nullptr;
 
 static uint16_t partitionBucketNumSystemPages(size_t size)
 {
@@ -1060,8 +1062,16 @@ void* partitionReallocGeneric(PartitionRootGeneric* root, void* ptr, size_t newS
         // We may be able to perform the realloc in place by changing the
         // accessibility of memory pages and, if reducing the size, decommitting
         // them.
-        if (partitionReallocDirectMappedInPlace(root, page, newSize))
+        if (partitionReallocDirectMappedInPlace(root, page, newSize)) {
+            // Report a realloc as a free followed by alloc when heap profiling
+            // is enabled.
+            if (UNLIKELY(PartitionHooks::allocationHook && PartitionHooks::freeHook)) {
+                PartitionHooks::freeHook(ptr);
+                PartitionHooks::allocationHook(ptr, newSize);
+            }
+
             return ptr;
+        }
     }
 
     size_t actualNewSize = partitionAllocActualSize(root, newSize);
@@ -1085,6 +1095,14 @@ void* partitionReallocGeneric(PartitionRootGeneric* root, void* ptr, size_t newS
 
     memcpy(ret, ptr, copySize);
     partitionFreeGeneric(root, ptr);
+
+    // Report a realloc as a free followed by alloc when heap profiling is
+    // enabled.
+    if (UNLIKELY(PartitionHooks::allocationHook && PartitionHooks::freeHook)) {
+        PartitionHooks::freeHook(ptr);
+        PartitionHooks::allocationHook(ret, newSize);
+    }
+
     return ret;
 #endif
 }