Condense namespaces in tint/transform.

This PR condenses the namespaces in the tint/transform folder.

Change-Id: Idf448870ccf90f892b9186f7aab7bb0ac9deda17
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/86029
Auto-Submit: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
diff --git a/src/tint/transform/combine_samplers.h b/src/tint/transform/combine_samplers.h
index f55c275..d15d2ab 100644
--- a/src/tint/transform/combine_samplers.h
+++ b/src/tint/transform/combine_samplers.h
@@ -21,8 +21,7 @@
 #include "src/tint/sem/sampler_texture_pair.h"
 #include "src/tint/transform/transform.h"
 
-namespace tint {
-namespace transform {
+namespace tint::transform {
 
 /// This transform converts all separate texture/sampler refences in a
 /// program into combined texture/samplers. This is required for GLSL,
@@ -104,7 +103,6 @@
            DataMap& outputs) const override;
 };
 
-}  // namespace transform
-}  // namespace tint
+}  // namespace tint::transform
 
 #endif  // SRC_TINT_TRANSFORM_COMBINE_SAMPLERS_H_