Incrementing VERSION to 70.0.3538.8

TBR=mmoss@chromium.org

Change-Id: I54dc29eb20958f3c3b7950b8b40cf64e91a8effe
Reviewed-on: https://chromium-review.googlesource.com/1207194
Reviewed-by: chrome-release-bot@chromium.org <chrome-release-bot@chromium.org>
Cr-Commit-Position: refs/branch-heads/3538@{#54}
Cr-Branched-From: 79f7c91-refs/heads/master@{#587811}

chrome/VERSION

@@ -1,4 +1,4 @@
 MAJOR=70
 MINOR=0
 BUILD=3538
-PATCH=7
+PATCH=8