Tweaking the draw-video-to-hw-accelerated-canvas-2d to stay on GPU

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 d4adbe96a4e9301b48c93b33eb457762f1076e59..f8d5945c3f32bac299cf5175d34ba4222a05c036 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
@@ -11,12 +11,11 @@ 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;
     destCanvas2D.height = height;
+    dummyCanvas2D.width = width;
+    dummyCanvas2D.height = height;
 }
 
 function startPerfTest() {
@@ -33,7 +32,9 @@ function doRun() {
 
 function ensureComplete() {
     // Using destCanvas2D as a source image is just to flush out the content when
-    // accelerated 2D canvas is in use. 
+    // accelerated 2D canvas is in use.
+    // dummyCtx2D must also be accelerated to prevent destCanvas2D from becoming
+    // non-accelerated due to the DisableAccelerationToAvoidReadbacks heuristic.
     dummyCtx2D.drawImage(destCanvas2D, 0, 0, 1, 1, 0, 0, 1, 1);
 }