Refactoring DrawLooper so that it can apply shadow effects as skia image filters

LayoutTests/fast/canvas/canvas-draw-canvas-on-canvas-shadow-expected.txt

Index: LayoutTests/fast/canvas/canvas-draw-canvas-on-canvas-shadow-expected.txt
diff --git a/LayoutTests/fast/canvas/canvas-draw-canvas-on-canvas-shadow-expected.txt b/LayoutTests/fast/canvas/canvas-draw-canvas-on-canvas-shadow-expected.txt
index 4711ea73060d9d4229e15c7784e9c6c2246bcca4..5b3196b2532b3d388f35a7e482edbe31e23be982 100644
--- a/LayoutTests/fast/canvas/canvas-draw-canvas-on-canvas-shadow-expected.txt
+++ b/LayoutTests/fast/canvas/canvas-draw-canvas-on-canvas-shadow-expected.txt
@@ -27,30 +27,30 @@ PASS d[0] is 255
 PASS d[1] is 0
 PASS d[2] is 0
 PASS d[3] is around 127
-FAIL d[0] should be 255. Was 0.
+PASS d[0] is 255
 PASS d[1] is 0
 PASS d[2] is 0
-FAIL d[3] is not around 100 (actual: 0)
-FAIL d[0] should be 255. Was 0.
+PASS d[3] is around 100
+PASS d[0] is 255
 PASS d[1] is 0
 PASS d[2] is 0
-FAIL d[3] is not around 100 (actual: 0)
-FAIL d[0] should be 255. Was 0.
+PASS d[3] is around 100
+PASS d[0] is 255
 PASS d[1] is 0
 PASS d[2] is 0
-FAIL d[3] is not around 100 (actual: 0)
-FAIL d[0] should be 255. Was 0.
+PASS d[3] is around 100
+PASS d[0] is 255
 PASS d[1] is 0
 PASS d[2] is 0
-FAIL d[3] is not around 50 (actual: 0)
-FAIL d[0] should be 255. Was 0.
+PASS d[3] is around 50
+PASS d[0] is 255
 PASS d[1] is 0
 PASS d[2] is 0
-FAIL d[3] is not around 50 (actual: 0)
-FAIL d[0] should be 255. Was 0.
+PASS d[3] is around 50
+PASS d[0] is 255
 PASS d[1] is 0
 PASS d[2] is 0
-FAIL d[3] is not around 50 (actual: 0)
+PASS d[3] is around 50
 PASS successfullyParsed is true
 
 TEST COMPLETE