Add bench to measure blur rects performance

gyp/bench.gypi

 {
   'include_dirs': [
     '../src/core',
     '../src/effects',
     '../src/gpu',
     '../src/utils',
     '../tools',
   ],
   'dependencies': [
     'etc1.gyp:libetc1',
@@ skipping 13 matching lines @@
 
     '../bench/AAClipBench.cpp',
     '../bench/AlternatingColorPatternBench.cpp',
     '../bench/BezierBench.cpp',
     '../bench/BitmapBench.cpp',
     '../bench/BitmapRectBench.cpp',
     '../bench/BitmapScaleBench.cpp',
     '../bench/BlurBench.cpp',
     '../bench/BlurImageFilterBench.cpp',
     '../bench/BlurRectBench.cpp',
+    '../bench/BlurRectsBench.cpp',
     '../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',
@@ skipping 54 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',
   ],
 }