Add a class to allocate small objects w/o extra calls to new.

gyp/tests.gypi

+# Common gypi for unit tests.
 {
   'include_dirs': [
     '../src/core',
     '../src/effects',
     '../src/image',
     '../src/lazy',
     '../src/images',
     '../src/pathops',
     '../src/pdf',
     '../src/pipe/utils',
@@ skipping 125 matching lines @@
     '../tests/RegionTest.cpp',
     '../tests/ResourceCacheTest.cpp',
     '../tests/RoundRectTest.cpp',
     '../tests/RuntimeConfigTest.cpp',
     '../tests/SHA1Test.cpp',
     '../tests/ScalarTest.cpp',
     '../tests/SerializationTest.cpp',
     '../tests/ShaderImageFilterTest.cpp',
     '../tests/ShaderOpacityTest.cpp',
     '../tests/SkBase64Test.cpp',
+    '../tests/SmallAllocatorTest.cpp',
     '../tests/SortTest.cpp',
     '../tests/SrcOverTest.cpp',
     '../tests/StreamTest.cpp',
     '../tests/StringTest.cpp',
     '../tests/StrokeTest.cpp',
     '../tests/SurfaceTest.cpp',
     '../tests/TLSTest.cpp',
     '../tests/TSetTest.cpp',
     '../tests/TestSize.cpp',
     '../tests/TileGridTest.cpp',
@@ skipping 16 matching lines @@
     '../src/utils/debugger/SkObjectParser.h',
     '../src/utils/debugger/SkObjectParser.cpp',
 
     '../tests/PipeTest.cpp',
     '../src/pipe/utils/SamplePipeControllers.cpp',
 
     '../tests/TDStackNesterTest.cpp',
     '../experimental/PdfViewer/src/SkTDStackNester.h',
   ],
 }