Merge "Speculative fix for crashes in HTMLImportsController::Dispose()." to M70 branch

Copy the loaders_ vector before iterating it.
This CL has no tests because we don't know stable reproduction.

Bug: 843151
Change-Id: I3d5e184657cbce56dcfca0c717d7a0c464e20efe
Reviewed-on: https://chromium-review.googlesource.com/1245017
Reviewed-by: Keishi Hattori <keishi@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#594226}(cherry picked from commit 54139dd9a60d8fb63d2379a08e2f2750eac2d959)
Reviewed-on: https://chromium-review.googlesource.com/c/1270199
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/branch-heads/3538@{#911}
Cr-Branched-From: 79f7c91a2b2a2932cd447fa6f865cb6662fa8fa6-refs/heads/master@{#587811}
1 file changed