[chromecast] Statically link libcast_media_default for media unittests.

chromecast/media/BUILD.gn

Index: chromecast/media/BUILD.gn
diff --git a/chromecast/media/BUILD.gn b/chromecast/media/BUILD.gn
index 4c4a87e2eaa0973c620049958f79307d79391d2c..832ea6430951166c9d039ae655d392c5a4c5cebb 100644
--- a/chromecast/media/BUILD.gn
+++ b/chromecast/media/BUILD.gn
@@ -57,4 +57,10 @@ test("cast_media_unittests") {
     "//testing/gtest",
     "//ui/gfx/geometry",
   ]
+
+  if (chromecast_branding == "public") {
+    # Link default libcast_media_1.0 statically not to link dummy one
+    # dynamically for public unittests.
+    deps += [ "//chromecast/media/base:libcast_media_1.0_default_core" ]
+  }
 }