Update nss_revision to 7b5b6ec41cf9105bd6e1c9a5157982f821282a4c.

Includes the following CLs:

Update to NSPR 4.10.7.
https://codereview.chromium.org/539213003/

R=rtenneti@chromium.org,zra@google.com
BUG=

Review URL: https://codereview.chromium.org/544743002

Cr-Commit-Position: refs/heads/master@{#293376}

DEPS

@@ -74,7 +74,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling nss
   # and whatever else without interference from each other.
-  'nss_revision': '90c5f9a8b8980fe60165813f578bbeb4fe20b18d',
+  'nss_revision': '7b5b6ec41cf9105bd6e1c9a5157982f821282a4c',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling google-toolbox-for-mac
   # and whatever else without interference from each other.