Fix PartitionAlloc cookies for large in-place reallocs

base/allocator/partition_allocator/partition_alloc.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/allocator/partition_allocator/partition_alloc.h"
 
 #include <string.h>
 
 #include "base/allocator/partition_allocator/oom.h"
 #include "base/allocator/partition_allocator/spin_lock.h"
@@ skipping 1033 matching lines @@
   }
 
   size_t actual_new_size = PartitionAllocActualSize(root, new_size);
   size_t actual_old_size = PartitionAllocGetSize(ptr);
 
   // TODO: note that tcmalloc will "ignore" a downsizing realloc() unless the
   // new size is a significant percentage smaller. We could do the same if we
   // determine it is a win.
   if (actual_new_size == actual_old_size) {
     // Trying to allocate a block of size new_size would give us a block of
-    // the same size as the one we've already got, so no point in doing
-    // anything here.
+    // the same size as the one we've already got, so re-use the allocation
+    // after updating statistics (and cookies, if present).
+    PartitionPageSetRawSize(page, PartitionCookieSizeAdjustAdd(new_size));
+#if DCHECK_IS_ON()
+    // Write a new trailing cookie.
+    PartitionCookieWriteValue(static_cast<char*>(ptr) + new_size);
+#endif
     return ptr;
   }
 
   // This realloc cannot be resized in-place. Sadness.
   void* ret = PartitionAllocGeneric(root, new_size, type_name);
   size_t copy_size = actual_old_size;
   if (new_size < copy_size)
     copy_size = new_size;
 
   memcpy(ret, ptr, copy_size);
@@ skipping 366 matching lines @@
     // can use PartitionAlloc to allocate and this can affect the statistics.
     for (size_t i = 0; i < partitionNumBuckets; ++i) {
       if (memory_stats[i].is_valid)
         dumper->PartitionsDumpBucketStats(partition_name, &memory_stats[i]);
     }
   }
   dumper->PartitionDumpTotals(partition_name, &stats);
 }
 
 }  // namespace base