Roll buildtools b73e5f0d7ac..dc487f429cb9 to roll GN 329298:330790.

List of changes:

https://chromium.googlesource.com/chromium/buildtools/+log/b73e5f70d7ac..dc487f429cb9

commit dc487f429cb90cac92ec7a9cd9d49db13648064d
Author: Dirk Pranke <dpranke@chromium.org>
Date:   Wed May 20 14:44:08 2015 -0700

    Roll GN 329298:330790 (c947c407..9d04333f)

    List of changes in tools/gn:

    https://chromium.googlesource.com/chromium/src/+log/c947c40710fe..9d04333fe102/tools/gn

    This roll mostly pulls in two new GN features:

    1) a new 'gn path' command for finding the dependencies
    linking two targets

    2) the 'runtime_deps' option to 'gn desc', which will compute
    the list of files needed to for a target to run based
    on the dependencies and data files listed on the targets. If
    --runtime-deps-list-file is specified when 'gn gen' is run,
    GN will also write out the dependencies for the targets listed
    in the file to $target.runtime_deps files.

    TBR=brettw@chromium.org
    BUG=480053

R=brettw@chromium.org
BUG=480053
CQ_EXTRA_TRYBOTS=tryserver.chromium.mac:mac_chromium_gn_rel;tryserver.chromium.win:win8_chromium_gn_rel

Review URL: https://codereview.chromium.org/1148283002

Cr-Commit-Position: refs/heads/master@{#330865}

DEPS

@@ -62,7 +62,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling build tools
   # and whatever else without interference from each other.
-  'buildtools_revision': 'b73e5f70d7ac6be98fb2555461f631afc90216ce',
+  'buildtools_revision': 'dc487f429cb90cac92ec7a9cd9d49db13648064d',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFium
   # and whatever else without interference from each other.