Fixing bad angle computation in 2D canvas arc rendering

LayoutTests/fast/canvas/bug503422.html

Index: LayoutTests/fast/canvas/bug503422.html
diff --git a/LayoutTests/fast/canvas/bug503422.html b/LayoutTests/fast/canvas/bug503422.html
new file mode 100644
index 0000000000000000000000000000000000000000..67209cfae51a1d6c41a071d63d50a5646624e1b9
--- /dev/null
+++ b/LayoutTests/fast/canvas/bug503422.html
@@ -0,0 +1,10 @@
+<p>Regression test for crbug.com/503422. Test passes by not crashing.</p>
+<canvas id=mycanvas width=400 height=400</script>
+<script>
+if (window.testRunner) {
+    testRunner.dumpAsText();
+}
+var canvas = document.getElementById('mycanvas');
+var ctx = canvas.getContext('2d');
+ctx.ellipse(80, 0, 10, 4294967277, Math.PI / -84, -Math.PI / 2147483436, false);
+</script>