Add benchmarks for 3 and 4 colors (most common)

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2143653002

Review-Url: https://codereview.chromium.org/2143653002
diff --git a/bench/HardStopGradientBench.cpp b/bench/HardStopGradientBench.cpp
index 7ebc51c..3a323fe 100644
--- a/bench/HardStopGradientBench.cpp
+++ b/bench/HardStopGradientBench.cpp
@@ -97,6 +97,8 @@
 };
 
 // Clamp
+DEF_BENCH(return new HardStopGradientBench(SkShader::kClamp_TileMode,   3);)
+DEF_BENCH(return new HardStopGradientBench(SkShader::kClamp_TileMode,   4);)
 DEF_BENCH(return new HardStopGradientBench(SkShader::kClamp_TileMode,   5);)
 DEF_BENCH(return new HardStopGradientBench(SkShader::kClamp_TileMode,  10);)
 DEF_BENCH(return new HardStopGradientBench(SkShader::kClamp_TileMode,  25);)
@@ -104,6 +106,8 @@
 DEF_BENCH(return new HardStopGradientBench(SkShader::kClamp_TileMode, 100);)
 
 // Repeat
+DEF_BENCH(return new HardStopGradientBench(SkShader::kRepeat_TileMode,   3);)
+DEF_BENCH(return new HardStopGradientBench(SkShader::kRepeat_TileMode,   4);)
 DEF_BENCH(return new HardStopGradientBench(SkShader::kRepeat_TileMode,   5);)
 DEF_BENCH(return new HardStopGradientBench(SkShader::kRepeat_TileMode,  10);)
 DEF_BENCH(return new HardStopGradientBench(SkShader::kRepeat_TileMode,  25);)
@@ -111,6 +115,8 @@
 DEF_BENCH(return new HardStopGradientBench(SkShader::kRepeat_TileMode, 100);)
 
 // Mirror
+DEF_BENCH(return new HardStopGradientBench(SkShader::kMirror_TileMode,   3);)
+DEF_BENCH(return new HardStopGradientBench(SkShader::kMirror_TileMode,   4);)
 DEF_BENCH(return new HardStopGradientBench(SkShader::kMirror_TileMode,   5);)
 DEF_BENCH(return new HardStopGradientBench(SkShader::kMirror_TileMode,  10);)
 DEF_BENCH(return new HardStopGradientBench(SkShader::kMirror_TileMode,  25);)