Disable canvas line dashing when dash sequence is all zeros.

third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-lineDash.js

 description("Basic test for setLineDash, getLineDash and lineDashOffset");
 
 var canvas = document.createElement('canvas');
 document.body.appendChild(canvas);
 canvas.setAttribute('width', '700');
 canvas.setAttribute('height', '700');
 var ctx = canvas.getContext('2d');
 
 function dataToArray(data) {
     var result = new Array(data.length)
@@ skipping 21 matching lines @@
 ctx.lineDashOffset = 5;
 ctx.strokeRect (10,10,100,100);
 
 // Verify dash and offset.
 var lineDash;
 lineDash = ctx.getLineDash();
 shouldBe('lineDash[0]', '15');
 shouldBe('lineDash[1]', '10');
 shouldBe('ctx.lineDashOffset', '5');
 
+// Verify setting line dash to sequence of nulls is interpreted as zeros
+ctx.setLineDash([null, null]);
+lineDash = ctx.getLineDash();
+shouldBe('lineDash[0]', '0');
+shouldBe('lineDash[1]', '0');
+
 // Set dash style to even number
 ctx.setLineDash([5, 10, 15]);
 ctx.strokeRect(20, 20, 120, 120);
 
 // Verify dash pattern is normalized
 lineDash = ctx.getLineDash();
 shouldBe('lineDash[0]', '5');
 shouldBe('lineDash[1]', '10');
 shouldBe('lineDash[2]', '15');
 shouldBe('lineDash[3]', '5');
@@ skipping 45 matching lines @@
 ctx.strokeRect(90.5, 10.5, 30, 30);
 pixelShouldBe(95, 10, [0, 0, 0, 0]);
 pixelShouldBe(105, 10, [0, 255, 0, 255]);
 pixelShouldBe(120, 15, [0, 0, 0, 0]);
 pixelShouldBe(120, 25, [0, 255, 0, 255]);
 pixelShouldBe(115, 40, [0, 0, 0, 0]);
 pixelShouldBe(105, 40, [0, 255, 0, 255]);
 pixelShouldBe(90, 35, [0, 0, 0, 0]);
 pixelShouldBe(90, 25, [0, 255, 0, 255]);
 
+// Verify that all zero dash sequence results in no dashing
+ctx.setLineDash([0, 0]);
+ctx.lineDashOffset = 0;
+ctx.strokeRect(130.5, 10.5, 30, 30);
+pixelShouldBe(130, 10, [0, 255, 0, 255]);
+pixelShouldBe(130, 15, [0, 255, 0, 255]);
+pixelShouldBe(130, 25, [0, 255, 0, 255]);
+pixelShouldBe(130, 35, [0, 255, 0, 255]);