tint: Add missing include

Should fix dawn -> chromium roll

Change-Id: If4bf1ed6795dc55c4c5a45e8ba8fa2eb0da7270a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/123521
Kokoro: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Reviewed-by: Stephen White <senorblanco@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: dan sinclair <dsinclair@google.com>
diff --git a/src/tint/writer/syntax_tree/generator_impl.cc b/src/tint/writer/syntax_tree/generator_impl.cc
index e5e2f2f..87d182e 100644
--- a/src/tint/writer/syntax_tree/generator_impl.cc
+++ b/src/tint/writer/syntax_tree/generator_impl.cc
@@ -34,6 +34,7 @@
 #include "src/tint/ast/workgroup_attribute.h"
 #include "src/tint/sem/struct.h"
 #include "src/tint/sem/switch_statement.h"
+#include "src/tint/switch.h"
 #include "src/tint/utils/math.h"
 #include "src/tint/utils/scoped_assignment.h"
 #include "src/tint/writer/float_to_string.h"