The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d8749fca8deac2969e2fe455b8c458de2e4b1e27

commit d8749fca8deac2969e2fe455b8c458de2e4b1e27
Author: rbpotter <rbpotter@chromium.org>
Date: Tue Oct 23 00:33:26 2018

Print Preview: Fix runtime errors with Polymer 2

Bug: 896748
Change-Id: I246e47b5791964dde5d7aa926c1c45c40541db03
Reviewed-on: https://chromium-review.googlesource.com/c/1294716
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601801}
[modify] https://crrev.com/d8749fca8deac2969e2fe455b8c458de2e4b1e27/chrome/browser/resources/print_preview/new/destination_settings.js
[modify] https://crrev.com/d8749fca8deac2969e2fe455b8c458de2e4b1e27/chrome/browser/resources/print_preview/new/model.js

The following CL should have been linked to this bug: https://crrev.com/c/1354639

This change is addressing some load time regressions from Polymer 1 to Polymer 2 by updating Polymer 2 to a new version (2.7.0) that was just released by the Polymer team. It contains some performance improvements that improve load times by 4-5% on some important user facing Web UI pages (settings, history, and Print Preview), bringing the performance closer to what it was with Polymer 1. Unfortunately, this update was not released until after the M72 branch cut, and Polymer 2 is enabled by default on 72 for non-Chrome OS platforms.

Consequently, requesting a merge for the CL linked above. Please advise if there is a better way to link it to this bug, now that it has already landed.

Your change meets the bar and is auto-approved for M72. Please go ahead and merge the CL to branch 3626 manually. Please contact milestone owner if you have questions.
Owners: govind@(Android), kariahda@(iOS), djmm@(ChromeOS), abdulsyed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bd25b2ffc374c8e039e1da227e761476b28999ba

commit bd25b2ffc374c8e039e1da227e761476b28999ba
Author: rbpotter <rbpotter@chromium.org>
Date: Fri Dec 07 18:30:01 2018

Web UI: Update Polymer 2 version to 2.7.0 (M72)

This improves load time for several Web UI pages with Polymer 2
by around 4-5%, which results in all tested pages having Polymer
2 load times within 8% of Polymer 1 load times.

Enabling the legacyOptimizations flag is responsible for over
half this improvement on chrome://print and chrome://history, and
seems to have little impact on other pages' performance.

Bug: 896748
Change-Id: I1bb776ad78d8c4972ed1925319c74ba9fd8c7d73
Reviewed-on: https://chromium-review.googlesource.com/c/1354639
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#613797}(cherry picked from commit 9cbb74720b74e9400f2780efda364231ec9c4d35)
Reviewed-on: https://chromium-review.googlesource.com/c/1367089
Cr-Commit-Position: refs/branch-heads/3626@{#141}
Cr-Branched-From: d897fb137fbaaa9355c0c93124cc048824eb1e65-refs/heads/master@{#612437}
[modify] https://crrev.com/bd25b2ffc374c8e039e1da227e761476b28999ba/third_party/polymer/v1_0/bower.json
[modify] https://crrev.com/bd25b2ffc374c8e039e1da227e761476b28999ba/third_party/polymer/v1_0/chromium.patch
[modify] https://crrev.com/bd25b2ffc374c8e039e1da227e761476b28999ba/third_party/polymer/v1_0/components-chromium/polymer2/bower.json
[modify] https://crrev.com/bd25b2ffc374c8e039e1da227e761476b28999ba/third_party/polymer/v1_0/components-chromium/polymer2/polymer-extracted.js
[modify] https://crrev.com/bd25b2ffc374c8e039e1da227e761476b28999ba/third_party/polymer/v1_0/components_summary.txt
[modify] https://crrev.com/bd25b2ffc374c8e039e1da227e761476b28999ba/ui/webui/resources/js/polymer_config.js

The following revision refers to this bug: 
https://chromium.googlesource.com/chromium/src.git/+/bd25b2ffc374c8e039e1da227e761476b28999ba

Commit: bd25b2ffc374c8e039e1da227e761476b28999ba
Author: rbpotter@chromium.org
Commiter: rbpotter@chromium.org
Date: 2018-12-07 18:30:01 +0000 UTC

Web UI: Update Polymer 2 version to 2.7.0 (M72)

This improves load time for several Web UI pages with Polymer 2
by around 4-5%, which results in all tested pages having Polymer
2 load times within 8% of Polymer 1 load times.

Enabling the legacyOptimizations flag is responsible for over
half this improvement on chrome://print and chrome://history, and
seems to have little impact on other pages' performance.

Bug: 896748
Change-Id: I1bb776ad78d8c4972ed1925319c74ba9fd8c7d73
Reviewed-on: https://chromium-review.googlesource.com/c/1354639
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#613797}(cherry picked from commit 9cbb74720b74e9400f2780efda364231ec9c4d35)
Reviewed-on: https://chromium-review.googlesource.com/c/1367089
Cr-Commit-Position: refs/branch-heads/3626@{#141}
Cr-Branched-From: d897fb137fbaaa9355c0c93124cc048824eb1e65-refs/heads/master@{#612437}