chromium: Update beta and dev channels.

Overview of the updated versions:

beta: 45.0.2454.15 -> 45.0.2454.26
dev:  45.0.2454.15 -> 46.0.2471.2

Changes for getting beta and dev channel to build:

 * The reference for chrome::FILE_FLASH_PLUGIN doesn't exist anymore in
   version 46, because it has been dropped upstream, see the following
   review URL:

   https://codereview.chromium.org/1255943002

   We set the PPAPI Flash path using a command line flag anyway, so it
   doesn't hurt us if we don't patch that path (which was an old
   artifact from the NSAPI->PPAPI conversion anyway).

Changes for the dev channel only:

 * It seems that in the SCM, chrome/test/data/webui/ contains a lot of
   files, however they are missing in the tarball.

   This has been reported upstream at: https://crbug.com/515917

   Our fix is to just not include webui/i18n_process_css_test.html at
   all, to avoid the configure (gyp) phase to fail, because we're not
   building tests anyway.

All channels built and tested by my Hydra instance at:

https://headcounter.org/hydra/eval/218978

Test reports:

x86:    https://headcounter.org/hydra/build/723341/download/1/log.html
x86_64: https://headcounter.org/hydra/build/723342/download/1/log.html



Signed-off-by: aszlig <aszlig@redmoonstudios.org>