add pathops tight bounds; conform path ops' gyp to unit tests

Implement path tight bounds using path ops machinery. This is not
as efficient as it could be; for instance, internally, it creates
a path ops structure more suited to intersection. If this shows
up as a performance bottleneck, it could be improved.

Fix path ops gyp files, which have fallen out of sync with other
tests.

R=mtklein@google.com, bsalomon@google.com
TBR=mtklein
BUG=skia:1712

Author: caryclark@google.com

Review URL: https://codereview.chromium.org/348343002
diff --git a/gyp/core.gypi b/gyp/core.gypi
index e1bdbd5..b4784bb 100644
--- a/gyp/core.gypi
+++ b/gyp/core.gypi
@@ -340,6 +340,7 @@
         '<(skia_src_path)/pathops/SkPathOpsQuad.cpp',
         '<(skia_src_path)/pathops/SkPathOpsRect.cpp',
         '<(skia_src_path)/pathops/SkPathOpsSimplify.cpp',
+        '<(skia_src_path)/pathops/SkPathOpsTightBounds.cpp',
         '<(skia_src_path)/pathops/SkPathOpsTriangle.cpp',
         '<(skia_src_path)/pathops/SkPathOpsTypes.cpp',
         '<(skia_src_path)/pathops/SkPathWriter.cpp',