GitLab

Currently the bindings overuse WrapperConfiguration::Dependent.
This changes it to use WrapperConfiguration::Independent
unless Dependent is actually needed, by computing it once
in the interface context.
(Fixes one FIXME and removes some hard-coding.)

This is split off as 1/2 bindings-only change from:
Implement ImageData constructors.
https://codereview.chromium.org/196343032/

BUG=345503
TBR=haraken

Review URL: https://codereview.chromium.org/199633014

git-svn-id: svn://svn.chromium.org/blink/trunk@169827 bbb929c8-8fbe-4397-9dbb-9b2b20218538