Fix edge case bugs of canvas arc.

LayoutTests/fast/canvas/canvas-arc-circumference-expected.txt

Index: LayoutTests/fast/canvas/canvas-arc-circumference-expected.txt
diff --git a/LayoutTests/fast/canvas/canvas-arc-circumference-expected.txt b/LayoutTests/fast/canvas/canvas-arc-circumference-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..81943ab365954e79de9e38250502b67f0f3a1144
--- /dev/null
+++ b/LayoutTests/fast/canvas/canvas-arc-circumference-expected.txt
@@ -0,0 +1,68 @@
+This tests checks that arc can draw correct circumferences with lineTo.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS imageData.data[1] is 255
+Check clockwise circumference.
+ 1. sweepAngle == 2PI
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+ 2. sweepAngle == PI
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 255
+PASS imageData.data[1] is 255
+ 3. sweepAngle > 2PI
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+ 4. sweepAngle < 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 255
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+Check anticlockwise circumference.
+ 1. sweepAngle == 2PI
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+ 2. sweepAngle == PI
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 255
+PASS imageData.data[1] is 255
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+ 3. sweepAngle > 2PI
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+ 4. sweepAngle < 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 0
+PASS imageData.data[1] is 255
+PASS successfullyParsed is true
+
+TEST COMPLETE
+