Fix issue that camera preview in account page is wrongly cropped

Adds 'resizeMode: none' in constraints to avoid being cropped
unexpectedly by Chrome.

Bug: b/148045035
Test: Manually
Change-Id: I4e2062cc75b438b1b64e7aa467b7c794a67cce95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2041213Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Wei Lee <wtlee@chromium.org>
Auto-Submit: Wei Lee <wtlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#739257}

ui/webui/resources/cr_elements/chromeos/cr_picture/cr_camera.js

@@ -168,6 +168,7 @@ Polymer({
       facingMode: 'user',
       width: {ideal: CAPTURE_SIZE.width},
       height: {ideal: CAPTURE_SIZE.height},
+      resizeMode: 'none',
     };
     navigator.webkitGetUserMedia(
         {video: videoConstraints}, successCallback, errorCallback);