Add an option to create unpremultiplied bitmaps.

gyp/bench.gypi

 # sources and conditions used in skia's bench.gyp and chromium's skia.gyp
 #
 {
   'sources': [
     '../bench/benchmain.cpp',
     '../bench/SkBenchmark.h',
     '../bench/SkBenchmark.cpp',
 
     '../bench/AAClipBench.cpp',
     '../bench/BicubicBench.cpp',
@@ skipping 10 matching lines @@
     '../bench/DashBench.cpp',
     '../bench/DecodeBench.cpp',
     '../bench/DeferredCanvasBench.cpp',
     '../bench/DeferredSurfaceCopyBench.cpp',
     '../bench/DisplacementBench.cpp',
     '../bench/FontCacheBench.cpp',
     '../bench/FontScalerBench.cpp',
     '../bench/GameBench.cpp',
     '../bench/GradientBench.cpp',
     '../bench/GrMemoryPoolBench.cpp',
+    '../bench/ImageDecodeBench.cpp',
     '../bench/InterpBench.cpp',
     '../bench/LineBench.cpp',
     '../bench/LightingBench.cpp',
     '../bench/MagnifierBench.cpp',
     '../bench/MathBench.cpp',
     '../bench/Matrix44Bench.cpp',
     '../bench/MatrixBench.cpp',
     '../bench/MatrixConvolutionBench.cpp',
     '../bench/MemoryBench.cpp',
     '../bench/MemsetBench.cpp',
@@ skipping 30 matching lines @@
     '../bench/TimerData.h',
     '../bench/TimerData.cpp',
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: