debian: Bump version to 19.2.0~cros1-4 for buster.

Unable to have the same version for stretch and buster, so do a version
bump for buster.

BUG=chromium:979461
TEST=buildpackages.sh

Change-Id: I7476793812502874fbb5da12b3a5cd1536d4161e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/mesa/+/1828336
Reviewed-by: Nicholas Verne <nverne@chromium.org>
Tested-by: David Riley <davidriley@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Commit-Queue: Stephen Barber <smbarber@chromium.org>
diff --git a/debian/changelog b/debian/changelog
index 3ebec29..f324603 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,4 +1,4 @@
-mesa (19.2.0~cros1-3) UNRELEASED; urgency=medium
+mesa (19.2.0~cros1-4) experimental; urgency=medium
 
   [ David Riley ]
   * Undo all comma striping from meson config flags.
@@ -6,7 +6,7 @@
   [ Nicholas Verne ]
   * Relax rules for override_dh_makeshlibs to c3 instead of c4
 
- -- Nicholas Verne <nverne@google.com>  Thu, 25 Jul 2019 08:02:19 +1000
+ -- David Riley <davidriley@google.com>  Thu, 26 Sep 2019 19:54:05 -0700
 
 mesa (19.2.0~cros1-1) experimental; urgency=medium