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/experimental/svg/model/SkSVGAttributeParser.cpp b/experimental/svg/model/SkSVGAttributeParser.cpp
index c23f9f1..4661500 100644
--- a/experimental/svg/model/SkSVGAttributeParser.cpp
+++ b/experimental/svg/model/SkSVGAttributeParser.cpp
@@ -30,7 +30,7 @@
     return is_ws(c) || c == ',' || c == ';';
 }
 
-} // anonymous ns
+}  // namespace
 
 SkSVGAttributeParser::SkSVGAttributeParser(const char attributeString[])
     : fCurPos(attributeString) {}