Add fixed revisions to bot_update json output.
Add fixed revisions to bot_update json output.

This will make all passed revisions appear in the json
output. This will make it easier/possible for recipes to
know after the step has run, which revisions were fixed
and which not.

This will help fixing the following scenario: A chromium
trybot that builds for component X will use:
bot_update -r src@HEAD -r src/X@HEAD

On retry after failure it currently uses:
bot_update -r src@got_revision -r src/X@HEAD

Instead it should use -r src/X@got_X_revision, as the
component repo might have changed during the run.
Currently, a fix isn't easy as the information, which
revisions are fixed, isn't passed around.

BUG=577130

Review URL: https://codereview.chromium.org/1582553002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@298265 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build