Enable ClangTidy check llvm-namespace-comment.

This fixes a large number of SkSL namespaces which were labeled as if
they were anonymous, and also a handful of other mislabeled namespaces.
Missing namespace-end comments have been added throughout.
A number of diffs are just indentation-related (adjusting 1- or 3-
space indents to 2-space).

Change-Id: I6c62052a0d3aea4ae12ca07e0c2a8587b2fce4ec
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/308503
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
diff --git a/src/utils/SkDashPathPriv.h b/src/utils/SkDashPathPriv.h
index 5c6a5db..3eaaef4 100644
--- a/src/utils/SkDashPathPriv.h
+++ b/src/utils/SkDashPathPriv.h
@@ -47,6 +47,6 @@
                         StrokeRecApplication = StrokeRecApplication::kAllow);
 
     bool ValidDashPath(SkScalar phase, const SkScalar intervals[], int32_t count);
-}
+}  // namespace SkDashPath
 
 #endif