LinearGradientContext::shade4_clamp: fix div by 0 getScaleX() may return 0; move division using it after a SkScalarNearlyZero check and closer to its first use. Change-Id: Ie209d46dc101213e20e90486651ee17570425bb8 Reviewed-on: https://skia-review.googlesource.com/4643 Reviewed-by: Florin Malita <fmalita@chromium.org> Commit-Queue: Florin Malita <fmalita@chromium.org>