Avoid int overflow in LinearGradientContext::shade4_dx_clamp

Change-Id: I86e01aa00b14f8a4b6e64169821768ab5ece9aa3
Reviewed-on: https://skia-review.googlesource.com/31481
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
1 file changed