replace SkFixedDiv impl with native 64bit math

bench/MathBench.cpp

Index: bench/MathBench.cpp
diff --git a/bench/MathBench.cpp b/bench/MathBench.cpp
index 5b46d1c704c835e6390a7df60ee50a03206cc5c4..e0d519407f4813c4bb96d2644b9c8ec541bf84ee 100644
--- a/bench/MathBench.cpp
+++ b/bench/MathBench.cpp
@@ -545,6 +545,50 @@ private:
 
 ///////////////////////////////////////////////////////////////////////////////
 
+class DivBitsBench : public Benchmark {
+protected:
+    enum {
+        N = 1000
+    };
+    volatile int32_t fSrc[N], fDst[N];
+public:
+    DivBitsBench() {
+        SkRandom rand;
+        for (int i = 0; i < N; ++i) {
+            fSrc[i] = rand.nextU();
+        }
+    }
+protected:
+    virtual void onDraw(const int loops, SkCanvas*) {
+        for (int j = 0; j < loops; ++j) {
+            for (int i = 0; i < N - 4; ++i) {
+                fDst[i] = SkDivBits(fSrc[i], fSrc[i] >> 3, 16);
+            }
+        }
+    }
+    virtual const char* onGetName() {
+        return "divbits";
+    }
+};
+DEF_BENCH( return new DivBitsBench; )
+
+class FixedDivBench : public DivBitsBench {
+protected:
+    virtual void onDraw(const int loops, SkCanvas*) {
+        for (int j = 0; j < loops; ++j) {
+            for (int i = 0; i < N - 4; ++i) {
+                fDst[i] = SkFixedDiv(fSrc[i], fSrc[i] >> 3);
+            }
+        }
+    }
+    virtual const char* onGetName() {
+        return "fixeddiv";
+    }
+};
+DEF_BENCH( return new FixedDivBench; )
+
+///////////////////////////////////////////////////////////////////////////////
+
 template <typename T>
 class DivModBench : public Benchmark {
     SkString fName;