vector: re-order some functions.

There are no code changes, just a re-ordering so that these files are
consistent with others in this package: OpOver, OpSrc, Mask.

Change-Id: Ib1d46a8e912dae0c760af655e919b77023688189
Reviewed-on: https://go-review.googlesource.com/30111
Reviewed-by: David Crawshaw <crawshaw@golang.org>

vector/raster_fixed.go

@@ -199,22 +199,6 @@ func (z *Rasterizer) fixedLineTo(b f32.Vec2) {
 	}
 }
 
-func fixedAccumulateOpSrc(dst []uint8, src []uint32) {
-	acc := int2ϕ(0)
-	for i, v := range src {
-		acc += int2ϕ(v)
-		a := acc
-		if a < 0 {
-			a = -a
-		}
-		a >>= 2*ϕ - 8
-		if a > 0xff {
-			a = 0xff
-		}
-		dst[i] = uint8(a)
-	}
-}
-
 func fixedAccumulateOpOver(dst []uint8, src []uint32) {
 	acc := int2ϕ(0)
 	for i, v := range src {
@@ -235,6 +219,22 @@ func fixedAccumulateOpOver(dst []uint8, src []uint32) {
 	}
 }
 
+func fixedAccumulateOpSrc(dst []uint8, src []uint32) {
+	acc := int2ϕ(0)
+	for i, v := range src {
+		acc += int2ϕ(v)
+		a := acc
+		if a < 0 {
+			a = -a
+		}
+		a >>= 2*ϕ - 8
+		if a > 0xff {
+			a = 0xff
+		}
+		dst[i] = uint8(a)
+	}
+}
+
 func fixedAccumulateMask(buf []uint32) {
 	acc := int2ϕ(0)
 	for i, v := range buf {

vector/raster_floating.go

@@ -145,21 +145,6 @@ const (
 	almost65536 = almost256 * 256
 )
 
-func floatingAccumulateOpSrc(dst []uint8, src []float32) {
-	acc := float32(0)
-	for i, v := range src {
-		acc += v
-		a := acc
-		if a < 0 {
-			a = -a
-		}
-		if a > 1 {
-			a = 1
-		}
-		dst[i] = uint8(almost256 * a)
-	}
-}
-
 func floatingAccumulateOpOver(dst []uint8, src []float32) {
 	acc := float32(0)
 	for i, v := range src {
@@ -179,6 +164,21 @@ func floatingAccumulateOpOver(dst []uint8, src []float32) {
 	}
 }
 
+func floatingAccumulateOpSrc(dst []uint8, src []float32) {
+	acc := float32(0)
+	for i, v := range src {
+		acc += v
+		a := acc
+		if a < 0 {
+			a = -a
+		}
+		if a > 1 {
+			a = 1
+		}
+		dst[i] = uint8(almost256 * a)
+	}
+}
+
 func floatingAccumulateMask(dst []uint32, src []float32) {
 	acc := float32(0)
 	for i, v := range src {