Comment 7 for bug 1702407

Thought I'd have a go out of interest - Replacing my new config dir with the old one reproduces the bug, but -dbg seems to require a previous verison of chromium-browser (had the the same problem trying to install -dbg from synaptic):

===
$ echo "deb http://ddebs.ubuntu.com $(lsb_release -cs) main restricted universe multiverse
> deb http://ddebs.ubuntu.com $(lsb_release -cs)-updates main restricted universe multiverse
> deb http://ddebs.ubuntu.com $(lsb_release -cs)-proposed main restricted universe multiverse" | \
> sudo tee -a /etc/apt/sources.list.d/ddebs.list
[sudo] password for user:
deb http://ddebs.ubuntu.com xenial main restricted universe multiverse
deb http://ddebs.ubuntu.com xenial-updates main restricted universe multiverse
deb http://ddebs.ubuntu.com xenial-proposed main restricted universe multiverse

$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 428D7C01 C8CAB6595FDFF622
Executing: /tmp/tmp.WR8LuQinDY/gpg.1.sh --keyserver
keyserver.ubuntu.com
--recv-keys
428D7C01
C8CAB6595FDFF622
gpg: requesting key 428D7C01 from hkp server keyserver.ubuntu.com
gpg: requesting key 5FDFF622 from hkp server keyserver.ubuntu.com
gpg: key 428D7C01: public key "Ubuntu Debug Symbol Archive Automatic Signing Key <email address hidden>" imported
gpg: key 5FDFF622: public key "Ubuntu Debug Symbol Archive Automatic Signing Key (2016) <email address hidden>" imported
gpg: Total number processed: 2
gpg: imported: 2 (RSA: 1)

$ sudo apt-get update

...
...

$ sudo apt-get install chromium-browser-dbg
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 chromium-browser-dbg : Depends: chromium-browser (= 51.0.2704.79-0ubuntu0.16.04.1.1242) but 59.0.3071.109-0ubuntu0.16.04.1289 is to be installed
E: Unable to correct problems, you have held broken packages.
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In case it helps, the version I had installed previously (at least according to my update logs) was chromium-browser (58.0.3029.110-0ubuntu0.16.04.1281)

Happy to help further if I can.