Update Dr. Memory to r2015

TBR=zhaoqin@chromium.org
BUG=https://code.google.com/p/drmemory/issues/detail?id=1584

Review URL: https://codereview.chromium.org/467963003

Cr-Commit-Position: refs/heads/master@{#289145}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289145 0039d316-1c4b-4281-b951-d872f2087c98

third_party/drmemory/README.chromium

 Name: Dr. Memory
 Short Name: drmemory
 URL: http://code.google.com/p/drmemory
-Version: 1.7.1983
+Version: 1.7.2015
 License: LGPL 2.1
 License File: NOT_SHIPPED
 Security Critical: no

third_party/drmemory/drmemory-windows-sfx.exe.sha1

-7c768ff82d66b09a47fc16c0c618e416780a9061
\ No newline at end of file
+f997295ea6768b666fac22d17cac57ead0dd26c0
\ No newline at end of file