Use testharness.js instead of js-test.js in LayoutTests/fast/canvas tests.

third_party/WebKit/LayoutTests/fast/canvas/canvas-blending-helpers.js

Index: third_party/WebKit/LayoutTests/fast/canvas/canvas-blending-helpers.js
diff --git a/third_party/WebKit/LayoutTests/fast/canvas/canvas-blending-helpers.js b/third_party/WebKit/LayoutTests/fast/canvas/canvas-blending-helpers.js
index af2885c0eabb3e45db0367402371b1b9bc5ef8f3..c0825df6f090bb98559b1c8cb8457bc62a327c4d 100644
--- a/third_party/WebKit/LayoutTests/fast/canvas/canvas-blending-helpers.js
+++ b/third_party/WebKit/LayoutTests/fast/canvas/canvas-blending-helpers.js
@@ -301,8 +301,12 @@ function nonSeparateBlendColors(backdrop, source, blendModeIndex) {
     return [Math.round(255 * expectedColor[0]), Math.round(255 * expectedColor[1]), Math.round(255 * expectedColor[2]), 255];
 }
 
-function checkBlendModeResult(i, context, sigma) {
-    var actualColor = context.getImageData(0, 0, 1, 1).data;
+function checkBlendModeResult(i, context, sigma, x, y) {
+    if (x === undefined)
+        x = 0;
+    if (y === undefined)
+        y = 0;
+    var actualColor = context.getImageData(x, y, 1, 1).data;
     var expectedColor = blendColors([129 / 255, 1, 129 / 255, 1], [1, 129 / 255, 129 / 255, 1], i);
     assert_approx_equals(actualColor[0], expectedColor[0], sigma);
     assert_approx_equals(actualColor[1], expectedColor[1], sigma);