Current implementation produces crashes since sometimes saved context
is empty. It looks like we do not need to restore saved context since
we do not set debug context as current, at least all tests are passed.

R=yangguo@chromium.org

Bug: chromium:797573,chromium:792838
Change-Id: I1271640f6a18cbaaecfa1e99ed9ac28e0dbbb1da
Reviewed-on: https://chromium-review.googlesource.com/844979Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50327}