Fix GCC warning in heap-profile-table.cc.

The current code throws the following warning:

../../third_party/tcmalloc/chromium/src/heap-profile-table.cc:522:42: warning:
  format '%lx' expects argument of type 'long unsigned int', but argument 4
  has type 'const void*' [-Wformat=]

BUG=None

Review URL: https://codereview.chromium.org/1180903010

Cr-Commit-Position: refs/heads/master@{#334813}
1 file changed