GN: Mark variables in nested scopes used for += and -=.

Previuosly GN would give an unused variable warning when you did += in an inner
scope for a variable defined in an outer scope. This patch marks the outer
variable used in this case.

Review-Url: https://codereview.chromium.org/2393853003
Cr-Original-Commit-Position: refs/heads/master@{#423226}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 80be99d1402bc09c858868b66761d2df77f218b3
2 files changed
tree: 7d3b84089ac48c489445f29b0ddae768230ab0fe
  1. tools/