added support for push_constant layout

gn/tests.gni

 # Copyright 2016 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Things are easiest for everyone if these source paths are absolute.
 _tests = get_path_info("../tests", "abspath")
 
 tests_sources = [
   "$_tests/AAClipTest.cpp",
@@ skipping 186 matching lines @@
   "$_tests/SkImageTest.cpp",
   "$_tests/SkLinearBitmapPipelineTest.cpp",
   "$_tests/SkLiteDLTest.cpp",
   "$_tests/SkNxTest.cpp",
   "$_tests/SkPEGTest.cpp",
   "$_tests/SkRasterPipelineTest.cpp",
   "$_tests/SkResourceCacheTest.cpp",
   "$_tests/SkSharedMutexTest.cpp",
   "$_tests/SkSLErrorTest.cpp",
   "$_tests/SkSLGLSLTest.cpp",
+  "$_tests/SkSLMemoryLayoutTest.cpp",
   "$_tests/SmallAllocatorTest.cpp",
   "$_tests/SortTest.cpp",
   "$_tests/SpecialImageTest.cpp",
   "$_tests/SpecialSurfaceTest.cpp",
   "$_tests/SrcOverTest.cpp",
   "$_tests/SRGBMipMapTest.cpp",
   "$_tests/SRGBReadWritePixelsTest.cpp",
   "$_tests/SRGBTest.cpp",
   "$_tests/StreamTest.cpp",
   "$_tests/StringTest.cpp",
@@ skipping 82 matching lines @@
   "$_tests/PathOpsSimplifyTest.cpp",
   "$_tests/PathOpsSimplifyTrianglesThreadedTest.cpp",
   "$_tests/PathOpsSkpTest.cpp",
   "$_tests/PathOpsTestCommon.cpp",
   "$_tests/PathOpsThreadedCommon.cpp",
   "$_tests/PathOpsThreeWayTest.cpp",
   "$_tests/PathOpsTigerTest.cpp",
   "$_tests/PathOpsTightBoundsTest.cpp",
   "$_tests/PathOpsTypesTest.cpp",
 ]