save/restore the canvas around every bench draw call

bench/BitmapBench.cpp

Index: bench/BitmapBench.cpp
diff --git a/bench/BitmapBench.cpp b/bench/BitmapBench.cpp
index a9b10f4669638d8c73783633ae420df33ea18381..982c917c02691319bc9a4b911c625b88d0f50066 100644
--- a/bench/BitmapBench.cpp
+++ b/bench/BitmapBench.cpp
@@ -363,7 +363,6 @@ DEF_BENCH( return new BitmapBench(true, SkBitmap::kIndex8_Config); )
 DEF_BENCH( return new BitmapBench(true, SkBitmap::kARGB_8888_Config, true, true); )
 DEF_BENCH( return new BitmapBench(true, SkBitmap::kARGB_8888_Config, true, false); )
 
-/* TODO(mtklein): figure out why these are broken (suspect caching is interfering) and restore
 // scale filter -> S32_opaque_D32_filter_DX_{SSE2,SSSE3} and Fact9 is also for S32_D16_filter_DX_SSE2
 DEF_BENCH( return new FilterBitmapBench(false, SkBitmap::kARGB_8888_Config, false, false, kScale_Flag | kBilerp_Flag); )
 DEF_BENCH( return new FilterBitmapBench(true, SkBitmap::kARGB_8888_Config, false, false, kScale_Flag | kBilerp_Flag); )
@@ -378,7 +377,6 @@ DEF_BENCH( return new FilterBitmapBench(true, SkBitmap::kARGB_8888_Config, true,
 
 DEF_BENCH( return new FilterBitmapBench(false, SkBitmap::kARGB_8888_Config, false, false, kScale_Flag | kBilerp_Flag | kBicubic_Flag); )
 DEF_BENCH( return new FilterBitmapBench(false, SkBitmap::kARGB_8888_Config, false, false, kScale_Flag | kRotate_Flag | kBilerp_Flag | kBicubic_Flag); )
-*/
 
 // source alpha tests -> S32A_Opaque_BlitRow32_{arm,neon}
 DEF_BENCH( return new SourceAlphaBitmapBench(SourceAlphaBitmapBench::kOpaque_SourceAlpha, SkBitmap::kARGB_8888_Config); )