As for searching for translated strings corresponding to IDS_FOO_BAR, what I do is to grep *en_GB.xtb files with (a substring of) the original message (en-US) because en-GB is almost identical to en-US to find out the corresponding xtb message id. 
Then, use that xtb message id to look for translated strings in other languages. 

Anyway, that should be a separate feature request. 

I forgot to list the flip-side (going from grd/grdp to C++ source files):

How to reproduce:

1. Go to a grd/grdp file with IDS_FOO_BAR
(e.g. https://goo.gl/1dTT2n : src/chrome/app/chromium_strings.grd )

2.  Try to click on IDS_MESSAGE_CENTER_TOOLTIP_UNREAD 

<message name="IDS_MESSAGE_CENTER_TOOLTIP_UNREAD" desc="Tooltip for notification tray icon with unread notifications">
          Chromium - Notifications (<ph name="QUANTITY">$1<ex>3</ex></ph> unread)
        </message>

Expected:

IDS_FOO_BAR is clickable and linked to C++ source files where that message is used. 

Actual: 
It's not a link. 

This is not a localization bug. Can't confirm that it's still relevant to the current English UI

Tested this issue on Mac 10.12.5 with chrome #61.0.3144.0 as per steps mentioned in comment #0.

Observed Only cc/h files are shown on clicking "IDS_BOOKMARK_EDITOR_CONFIRM_DELETE"

Attaching the screen-cast for reference.

Deleted: 613347.mp4 3.1 MB

	613347.mp4 3.1 MB View Download

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I think this would require implementing a custom cross-reference parser and adding support for a new language to Kythe, which is infeasible in the near future.