Revert of Update V8 to version 3.27.17 (based on bleeding_edge revision...

Revert of Update V8 to version 3.27.17 (based on bleeding_edge revision r21586) (https://codereview.chromium.org/303263007/)

Reason for revert:
gn config doesn't work

Original issue's description:
> Update V8 to version 3.27.17 (based on bleeding_edge revision r21586)
> 
> R=mvstanton@chromium.org
> TBR=mvstanton@chromium.org
> BUG=none
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=274195

TBR=mvstanton@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=none

Review URL: https://codereview.chromium.org/304313005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@274202 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -50,7 +50,7 @@ vars = {
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.
   "v8_branch": "trunk",
-  "v8_revision": "21587",
+  "v8_revision": "21543",
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling WebRTC
   # and V8 without interference from each other.