Add GrSet class built on top of RedBlackTree

BUG=skia:
R=bsalomon@google.com

Author: egdaniel@google.com

Review URL: https://codereview.chromium.org/176903003

git-svn-id: http://skia.googlecode.com/svn/trunk@13616 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/tests.gypi b/gyp/tests.gypi
index f5143e2..779ffde 100644
--- a/gyp/tests.gypi
+++ b/gyp/tests.gypi
@@ -88,6 +88,7 @@
     '../tests/GrDrawTargetTest.cpp',
     '../tests/GrMemoryPoolTest.cpp',
     '../tests/GrRedBlackTreeTest.cpp',
+    '../tests/GrOrderedSetTest.cpp',
     '../tests/GrSurfaceTest.cpp',
     '../tests/GrTBSearchTest.cpp',
     '../tests/GradientTest.cpp',