Refactor SkPictureStateTree::Iterator to avoid use of kClip_SaveFlag.

gyp/tests.gypi

 # Common gypi for unit tests.
 {
   'include_dirs': [
     '../src/core',
     '../src/effects',
     '../src/image',
     '../src/lazy',
     '../src/images',
     '../src/pathops',
     '../src/pdf',
@@ skipping 111 matching lines @@
     '../tests/PDFPrimitivesTest.cpp',
     '../tests/PackBitsTest.cpp',
     '../tests/PaintTest.cpp',
     '../tests/ParsePathTest.cpp',
     '../tests/PathCoverageTest.cpp',
     '../tests/PathMeasureTest.cpp',
     '../tests/PathTest.cpp',
     '../tests/PathUtilsTest.cpp',
     '../tests/PictureTest.cpp',
     '../tests/PictureShaderTest.cpp',
+    '../tests/PictureStateTreeTest.cpp',
     '../tests/PictureUtilsTest.cpp',
     '../tests/PixelRefTest.cpp',
     '../tests/PointTest.cpp',
     '../tests/PremulAlphaRoundTripTest.cpp',
     '../tests/QuickRejectTest.cpp',
     '../tests/RTreeTest.cpp',
     '../tests/RandomTest.cpp',
     '../tests/ReadPixelsTest.cpp',
     '../tests/ReadWriteAlphaTest.cpp',
     '../tests/Reader32Test.cpp',
@@ skipping 48 matching lines @@
 
     '../tests/PipeTest.cpp',
     '../src/pipe/utils/SamplePipeControllers.cpp',
 
     '../tests/TDStackNesterTest.cpp',
     '../experimental/PdfViewer/src/SkTDStackNester.h',
 
     '../tools/sk_tool_utils.cpp',
   ],
 }