Comment 1 for bug 1653239

It appears that the the line in the debian/rules file that should take care of this did not work properly in the package that I downloaded from the repository....

Here is the line from the rules file:
 cat debian/10-flash.in | sed -e 's/#PPAPI_VERSION#/$(shell python -c "import json; print json.load(file('$(DEB_BUILD_ARCH)/manifest.json'))['version']")/g' > debian/10-flash

Here is the output when I rebuilt using a clean sbuild environment:
cat debian/10-flash.in | sed -e 's/#PPAPI_VERSION#/24.0.0.186/g' > debian/10-flash

The file /etc/chromium-browser/customizations/10-flash appears to be correct when I build the package without changes in a pristine sbuild environment created with
mk-sbuild trusty --arch=amd64 --name=tester --debootstrap-mirror=http://us.archive.ubuntu.com/ubuntu --distro=ubuntu --vg data

It looks as if there is something missing in the build environment that is not specified in the control file used to build adobe-flashplugin 1:20161213.1-0ubuntu0.