--- a/testing/marionette/capture.js
+++ b/testing/marionette/capture.js
@@ -39,17 +39,17 @@ capture.element = function (node, highli
   let rect = node.getBoundingClientRect();
 
   return capture.canvas(
       win,
       rect.left,
       rect.top,
       rect.width,
       rect.height,
-      highlights);
+      {highlights});
 };
 
 /**
  * Take a screenshot of the window's viewport by taking into account
  * the current offsets.
  *
  * @param {DOMWindow} win
  *     The DOM window providing the document element to capture,
@@ -65,17 +65,17 @@ capture.viewport = function (win, highli
   let rootNode = win.document.documentElement;
 
   return capture.canvas(
       win,
       win.pageXOffset,
       win.pageYOffset,
       rootNode.clientWidth,
       rootNode.clientHeight,
-      highlights);
+      {highlights});
 };
 
 /**
  * Low-level interface to draw a rectangle off the framebuffer.
  *
  * @param {DOMWindow} win
  *     The DOM window used for the framebuffer, and providing the interfaces
  *     for creating an HTMLCanvasElement.
@@ -85,27 +85,31 @@ capture.viewport = function (win, highli
  *     The top, Y axis offset of the rectangle.
  * @param {number} width
  *     The width dimension of the rectangle to paint.
  * @param {number} height
  *     The height dimension of the rectangle to paint.
  * @param {Array.<Node>=} highlights
  *     Optional array of nodes, around which a border will be marked to
  *     highlight them in the screenshot.
+ * @param {HTMLCanvasElement=} canvas
+ *     Optional canvas to reuse for the screenshot.
  *
  * @return {HTMLCanvasElement}
  *     The canvas on which the selection from the window's framebuffer
  *     has been painted on.
  */
-capture.canvas = function (win, left, top, width, height, highlights = []) {
+capture.canvas = function (win, left, top, width, height, {highlights = [], canvas = null} = {}) {
   let scale = win.devicePixelRatio;
 
-  let canvas = win.document.createElementNS(XHTML_NS, "canvas");
-  canvas.width = width * scale;
-  canvas.height = height * scale;
+  if (canvas === null) {
+    canvas = win.document.createElementNS(XHTML_NS, "canvas");
+    canvas.width = width * scale;
+    canvas.height = height * scale;
+  }
 
   let ctx = canvas.getContext(CONTEXT_2D);
   let flags = ctx.DRAWWINDOW_DRAW_CARET;
       // Disabled in bug 1243415 for webplatform-test failures due to out of view elements.
       // Needs https://github.com/w3c/web-platform-tests/issues/4383 fixed.
       // ctx.DRAWWINDOW_DRAW_VIEW;
       // Bug 1009762 - Crash in [@ mozilla::gl::ReadPixelsIntoDataSurface]
       // ctx.DRAWWINDOW_USE_WIDGET_LAYERS;
@@ -185,9 +189,9 @@ function hex(buffer) {
   for (let i = 0; i < view.byteLength; i += 4) {
     let value = view.getUint32(i);
     let stringValue = value.toString(16);
     let padding = '00000000';
     let paddedValue = (padding + stringValue).slice(-padding.length);
     hexCodes.push(paddedValue);
   }
   return hexCodes.join("");
-};
\ No newline at end of file
+};