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* Enables reporting of  user-mode debugging to debug
  DevToolsPerContextListeners.
* Remove DISALLOW_COPY_AND_ASSIGN in WebEngineDevToolsController
  implementations.
* Add test enabling both user and debug-mode debugging.

Bug: 1018371
Change-Id: Ie38c1c9318190e1e9c374f9ccf86a749aa531027
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1898473
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715018}