Fix canvas blink_perf tests to avoid GPU fallback

third_party/WebKit/PerformanceTests/Canvas/draw-video-to-hw-accelerated-canvas-2d.html

Index: third_party/WebKit/PerformanceTests/Canvas/draw-video-to-hw-accelerated-canvas-2d.html
diff --git a/third_party/WebKit/PerformanceTests/Canvas/draw-video-to-hw-accelerated-canvas-2d.html b/third_party/WebKit/PerformanceTests/Canvas/draw-video-to-hw-accelerated-canvas-2d.html
index 783a3d3700f764399dfdfb8ed3f7705cf22f5587..d4adbe96a4e9301b48c93b33eb457762f1076e59 100644
--- a/third_party/WebKit/PerformanceTests/Canvas/draw-video-to-hw-accelerated-canvas-2d.html
+++ b/third_party/WebKit/PerformanceTests/Canvas/draw-video-to-hw-accelerated-canvas-2d.html
@@ -8,6 +8,11 @@
 var videoElement = document.getElementById("video");
 var destCanvas2D = document.createElement("canvas");
 var destCtx2D = destCanvas2D.getContext("2d");
+var dummyCanvas2D = document.createElement("canvas");
+var dummyCtx2D = dummyCanvas2D.getContext("2d");
+
+dummyCanvas2D.width = 1;
+dummyCanvas2D.height = 1;
 
 function setSize(width, height) {
     destCanvas2D.width = width;
@@ -27,9 +32,9 @@ function doRun() {
 }
 
 function ensureComplete() {
-    // Calling getImageData() is just to flush out the content when
-    // accelerated 2D canvas is in use. The cost of reading 1x1 pixels is low.
-    destCtx2D.getImageData(0, 0, 1, 1);
+    // Using destCanvas2D as a source image is just to flush out the content when
+    // accelerated 2D canvas is in use. 
+    dummyCtx2D.drawImage(destCanvas2D, 0, 0, 1, 1, 0, 0, 1, 1);
 }
 
 window.onload = function () {