Include svn revision range in Blink roll descriptions.

Include svn revision range in Blink roll descriptions.

Prior to http://crrev.com/495493003, Blink rolls had the Blink svn revision range in their descriptions, which made it easy to determine which roll contained a given revision number by scanning the log of src/DEPS.  To do this with git hashes is much more difficult since they are not sequential and cannot be compared at a glance.

This change adds the svn range even when git_mode is True.  The resulting descriptions look like:

  Blink roll hash1:hash2 (svn 1234:1235)

TBR=szager@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=291939

[skobes, 2014-09-11 22:14:55]

This change was reviewed in https://codereview.chromium.org/559243002.  Trying
to commit in a new Rietveld issue.

[skobes, 2014-09-11 22:15:00]

The CQ bit was checked by skobes@chromium.org

[commit-bot: I haz the power, 2014-09-11 22:16:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/568593002/1

[commit-bot: I haz the power, 2014-09-11 22:17:36]

Committed patchset #1 (id:1) as 291939