Fixing nits in canvas-perf

Since Math.random() in python generates a random number in range [0,1),
we need to use rand(256) to generate number [0, 255]. Update all calls
in canvas perftest to call rand(256).

Bug:1087019

Change-Id: I75ded3269cf652d7d352e32eefbfeddb999583b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2216736
Commit-Queue: Yi Xu <yiyix@chromium.org>
Reviewed-by: Juanmi Huertas <juanmihd@chromium.org>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772294}

third_party/blink/perf_tests/canvas/canvas-to-canvas-draw.html

@@ -26,7 +26,7 @@ function rand(range) {
 }
 
 function randomColor() {
-  return "rgba(" + rand(255) + "," + rand(255) + "," + rand(255)  + "," + rand(255) + ")";
+  return "rgba(" + rand(256) + "," + rand(256) + "," + rand(256)  + "," + rand(256) + ")";
 }
 
 function makeAndFillCanvasWithRandomColor(i) {

third_party/blink/perf_tests/canvas/draw-dynamic-canvas-2d-to-hw-accelerated-canvas-2d.html

@@ -25,7 +25,7 @@ function rand(range) {
 }
 
 function fillCanvas(ctx2d, canvas2d) {
-    ctx2d.fillStyle = "rgba(" + rand(255) + "," + rand(255) + "," + rand(255)  + "," + rand(255) + ")";
+    ctx2d.fillStyle = "rgba(" + rand(256) + "," + rand(256) + "," + rand(256)  + "," + rand(256) + ")";
     ctx2d.fillRect(0, 0, canvas2d.width, canvas2d.height);
 }
 

third_party/blink/perf_tests/canvas/draw-hw-accelerated-canvas-2d-to-sw-canvas-2d.html

@@ -25,7 +25,7 @@ function rand(range) {
 }
 
 function fillCanvas(ctx2d, canvas2d) {
-    ctx2d.fillStyle = "rgba(" + rand(255) + "," + rand(255) + "," + rand(255)  + "," + rand(255) + ")";
+    ctx2d.fillStyle = "rgba(" + rand(256) + "," + rand(256) + "," + rand(256)  + "," + rand(256) + ")";
     ctx2d.fillRect(0, 0, canvas2d.width, canvas2d.height);
 }
 

third_party/blink/perf_tests/canvas/draw-static-canvas-2d-to-hw-accelerated-canvas-2d.html

@@ -25,7 +25,7 @@ function rand(range) {
 }
 
 function fillCanvas(ctx2d, canvas2d) {
-    ctx2d.fillStyle = "rgba(" + rand(255) + "," + rand(255) + "," + rand(255)  + "," + rand(255) + ")";
+    ctx2d.fillStyle = "rgba(" + rand(256) + "," + rand(256) + "," + rand(256)  + "," + rand(256) + ")";
     ctx2d.fillRect(0, 0, canvas2d.width, canvas2d.height);
 }
 

third_party/blink/perf_tests/canvas/getImageData.html

@@ -17,7 +17,7 @@ function rand(range) {
 }
 
 function fillCanvas(ctx2d, canvas2d) {
-    ctx2d.fillStyle = "rgba(" + rand(255) + "," + rand(255) + "," + rand(255)  + "," + rand(255) + ")";
+    ctx2d.fillStyle = "rgba(" + rand(256) + "," + rand(256) + "," + rand(256)  + "," + rand(256) + ")";
     ctx2d.fillRect(0, 0, canvas2d.width, canvas2d.height);
 }
 

third_party/blink/perf_tests/canvas/upload-canvas-2d-to-texture.html

@@ -25,7 +25,7 @@ function rand(range) {
 }
 
 function fillCanvas(ctx2d, canvas2d) {
-    ctx2d.fillStyle = "rgba(" + rand(255) + "," + rand(255) + "," + rand(255)  + "," + rand(255) + ")";
+    ctx2d.fillStyle = "rgba(" + rand(256) + "," + rand(256) + "," + rand(256)  + "," + rand(256) + ")";
     ctx2d.fillRect(0, 0, canvas2d.width, canvas2d.height);
 }