Bug 1289549 bump slop in jpg color test, r=maglione

MozReview-Commit-ID: GGNze65Lpkl

browser/components/extensions/test/browser/browser_ext_tabs_captureVisibleTab.js

@@ -95,7 +95,7 @@ function* runTest(options) {
               browser.test.assertEq(`rgba(${color},255)`, `rgba(${[...imageData]})`, `${format} image color is correct at (${x}, ${y})`);
             } else {
               // Allow for some deviation in JPEG version due to lossy compression.
-              const SLOP = 2;
+              const SLOP = 3;
 
               browser.test.log(`Testing ${format} image color at (${x}, ${y}), have rgba(${[...imageData]}), expecting approx. rgba(${color},255)`);