Handle SkBitmaps which have no pixels in SkPDFImage.

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 129 matching lines @@
     '../tests/MatrixClipCollapseTest.cpp',
     '../tests/MatrixTest.cpp',
     '../tests/MemoryTest.cpp',
     '../tests/MemsetTest.cpp',
     '../tests/MessageBusTest.cpp',
     '../tests/MetaDataTest.cpp',
     '../tests/MipMapTest.cpp',
     '../tests/NameAllocatorTest.cpp',
     '../tests/OSPathTest.cpp',
     '../tests/OnceTest.cpp',
+    '../tests/PDFInvalidBitmapTest.cpp',
     '../tests/PDFJpegEmbedTest.cpp',
     '../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/PictureBBHTest.cpp',
@@ skipping 66 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',
   ],
 }