Roll src/third_party/depot_tools/ e117e46a6..2b51c930e (9 commits; 2 trivial rolls)

https://chromium.googlesource.com/chromium/tools/depot_tools.git/+log/e117e46a6894..2b51c930e009

$ git log e117e46a6..2b51c930e --date=short --no-merges --format='%ad %ae %s'
2018-02-07 tandrii Revert "bot_update: allow rebasing the patch onto an older revision."
2018-02-06 iannucci [luci-auth] Add statically-linked luci-auth CLI tool.
2018-02-06 iannucci [prpc] Add pRPC CLI tool to depot_tools.
2018-02-06 tandrii bot_update: optimize checkout of solution's main repo.
2018-02-06 thomasanderson Add target_cpu builtin variable to gclient
2018-02-06 oprypin bot_update: allow rebasing the patch onto an older revision.
2018-02-05 mmoss Make flattened recursedeps inherit parent conditionals.

Created with:
  roll-dep src/third_party/depot_tools
BUG=807986,783607


The AutoRoll server is located here: https://depot-tools-chromium-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.


TBR=agable@chromium.org

Change-Id: I2db4866326042b36e2d166db3cfd0740dcb639ec
Reviewed-on: https://chromium-review.googlesource.com/905932
Commit-Queue: depot-tools-chromium-autoroll <depot-tools-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Reviewed-by: depot-tools-chromium-autoroll <depot-tools-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#534909}

DEPS

@@ -336,7 +336,7 @@ deps = {
   },
 
   'src/third_party/depot_tools':
-    Var('chromium_git') + '/chromium/tools/depot_tools.git' + '@' + 'e117e46a6894979f85f6329dcb04c945a93f37d8',
+    Var('chromium_git') + '/chromium/tools/depot_tools.git' + '@' + '2b51c930e009ff0facd2b04af3975a826eef0a23',
 
   'src/third_party/devtools-node-modules':
     Var('chromium_git') + '/external/github.com/ChromeDevTools/devtools-node-modules' + '@' + Var('devtools_node_modules_revision'),