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This CL adds getter/setter for colour temperature for
Android implementation.  JS API uses Kelvin grades,
whereas the platform uses names, so a mapping of
sorts is introduced.

BUG=650675
TEST= by hand using the JS ImageCapture API.

Review-Url: https://codereview.chromium.org/2385833002
Cr-Commit-Position: refs/heads/master@{#422832}