Adding new benchmark to test image decoding performance.

gyp/bench.gypi

 {
   'include_dirs': [
     '../src/core',
     '../src/effects',
     '../src/gpu',
     '../src/utils',
     '../tools',
   ],
   'dependencies': [
     'etc1.gyp:libetc1',
@@ skipping 25 matching lines @@
     '../bench/BlurRoundRectBench.cpp',
     '../bench/ChartBench.cpp',
     '../bench/ChecksumBench.cpp',
     '../bench/ChromeBench.cpp',
     '../bench/CmapBench.cpp',
     '../bench/ColorCubeBench.cpp',
     '../bench/ColorFilterBench.cpp',
     '../bench/ColorPrivBench.cpp',
     '../bench/CoverageBench.cpp',
     '../bench/DashBench.cpp',
-    '../bench/DecodeBench.cpp',
     '../bench/DeferredSurfaceCopyBench.cpp',
     '../bench/DisplacementBench.cpp',
     '../bench/ETCBitmapBench.cpp',
     '../bench/FSRectBench.cpp',
     '../bench/FontCacheBench.cpp',
     '../bench/FontScalerBench.cpp',
     '../bench/GameBench.cpp',
     '../bench/GeometryBench.cpp',
     '../bench/GrMemoryPoolBench.cpp',
     '../bench/GrResourceCacheBench.cpp',
     '../bench/GrOrderedSetBench.cpp',
     '../bench/GradientBench.cpp',
     '../bench/HairlinePathBench.cpp',
     '../bench/ImageCacheBench.cpp',
-    '../bench/ImageDecodeBench.cpp',
     '../bench/ImageFilterDAGBench.cpp',
     '../bench/ImageFilterCollapse.cpp',
     '../bench/InterpBench.cpp',
     '../bench/LightingBench.cpp',
     '../bench/LineBench.cpp',
     '../bench/MagnifierBench.cpp',
     '../bench/MathBench.cpp',
     '../bench/Matrix44Bench.cpp',
     '../bench/MatrixBench.cpp',
     '../bench/MatrixConvolutionBench.cpp',
@@ skipping 30 matching lines @@
     '../bench/StrokeBench.cpp',
     '../bench/TableBench.cpp',
     '../bench/TextBench.cpp',
     '../bench/TileBench.cpp',
     '../bench/VertBench.cpp',
     '../bench/WritePixelsBench.cpp',
     '../bench/WriterBench.cpp',
     '../bench/XfermodeBench.cpp',
   ],
 }