Roll src/third_party/cros_system_api/ 7d1c88ce9..557c37af3 (2 commits)

https://chromium.googlesource.com/chromiumos/platform/system_api.git/+log/7d1c88ce942e..557c37af39f5

$ git log 7d1c88ce9..557c37af3 --date=short --no-merges --format='%ad %ae %s'
2018-06-14 benchan shill: add DHCPProperty.Hostname and DHCPProperty.VendorClass property
2018-06-12 smbarber vm_cicerone: add ipv4_address to NotifyVmStartedRequest

Created with:
  roll-dep src/third_party/cros_system_api

Change-Id: Icadccd2f79faf69e30d19dbbd5e35f0eb35c0c18
Reviewed-on: https://chromium-review.googlesource.com/1103708Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568062}

DEPS

@@ -533,7 +533,7 @@ deps = {
 
   # For Linux and Chromium OS.
   'src/third_party/cros_system_api': {
-      'url': Var('chromium_git') + '/chromiumos/platform/system_api.git' + '@' + '7d1c88ce942e8fcaf130ab2d595280b9c910e864',
+      'url': Var('chromium_git') + '/chromiumos/platform/system_api.git' + '@' + '557c37af39f5195d80aaad53c3a06b5ec804da95',
       'condition': 'checkout_linux',
   },