Add AtkValue support on meter element

* Add ax::mojom::Role::kMeter to the roles which support AtkValue
* Include minimum, maximum, and current values to information output
  by DumpAccessibility* tests

Bug: 944125
Change-Id: Iaa3871d9494aa391e2f5328f96e99d8d2339b3ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1532921
Reviewed-by: Martin Robinson <mrobinson@igalia.com>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Joanmarie Diggs <joanmarie.diggs@gmail.com>
Cr-Original-Commit-Position: refs/heads/master@{#643009}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 4c7a218a2be83f7de6a526d4dc3bebcc7db17349

config/linux/atk/BUILD.gn

@@ -30,6 +30,12 @@ pkg_config("atk_base") {
   defines = [
     "ATK_LIB_DIR=\"$atk_lib_dir\"",
     "USE_ATK_BRIDGE",
+
+    # The AtkValue interface methods we implement and test have been deprecated
+    # in favor of new API. But that new API cannot be used until corresponding
+    # support has been added to AT-SPI2 and we stop supporting earlier versions
+    # of ATK (i.e. < 2.12).
+    "ATK_DISABLE_DEPRECATION_WARNINGS",
   ]
 }