Updates for things I ran into while running clang-tidy locally.

* Make ui/views/.clang-tidy additive to the base file, not a
  replacement.
* Hoist the "use equals" config option to the base file, since that's
  Chromium style.
* Update docs for errors or inclarities.

Bug: none
Change-Id: I7f22db99d9ff11fc91665776887a02f7184427ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2483344
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Commit-Queue: George Burgess <gbiv@chromium.org>
Reviewed-by: George Burgess <gbiv@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818330}

.clang-tidy

----
 ---
   Checks:          '-*,
                     bugprone-string-integer-assignment,
@@ -25,6 +24,8 @@
                     modernize-use-transparent-functors,
                     readability-redundant-member-init'
   CheckOptions:
+    - key:          modernize-use-default-member-init.UseAssignment
+      value:        1
     # This relaxes modernize-use-emplace in some cases; we might want to make it
     # more aggressive in the future. See discussion on
     # https://groups.google.com/a/chromium.org/g/cxx/c/noMMTNYiM0w .

docs/clang_tidy.md

@@ -75,7 +75,7 @@ clang-tidy across all of Chromium is a single command:
 
 ```
 $ cd ${chromium}/src
-$ ${chromium_build}/scripts/slave/recipe_modules/tricium_clang_tidy/resources/tricium_clang_tidy.py \
+$ ${chromium_build}/recipes/recipe_modules/tricium_clang_tidy/resources/tricium_clang_tidy.py \
     --base_path $PWD \
     --out_dir out/Linux \
     --findings_file all_findings.json \
@@ -212,7 +212,7 @@ gn gen . --export-compile-commands
 ```
 4.  Run clang-tidy.
 ```
-<PATH_TO_LLVM_SRC>/clang-tidy/tool/run-clang-tidy.py \
+<PATH_TO_LLVM_SRC>/clang-tools-extra/clang-tidy/tool/run-clang-tidy.py \
     -p . \# Set the root project directory, where compile_commands.json is.
     # Set the clang-tidy binary path, if it's not in your $PATH.
     -clang-tidy-binary <PATH_TO_LLVM_BUILD>/bin/clang-tidy \
@@ -220,11 +220,11 @@ gn gen . --export-compile-commands
     # and you are using the `fix` behavior of clang-tidy.
     -clang-apply-replacements-binary \
         <PATH_TO_LLVM_BUILD>/bin/clang-apply-replacements \
-    # The checks to employ in the build. Use `-*` to omit default checks.
+    # The checks to employ in the build. Use `-*,...` to omit default checks.
     -checks=<CHECKS> \
     -header-filter=<FILTER> \# Optional, limit results to only certain files.
     -fix \# Optional, used if you want to have clang-tidy auto-fix errors.
-    chrome/browser # The path to the files you want to check.
+    'chrome/browser/.*' # A regex of the files you want to check.
 
 Copy-Paste Friendly (though you'll still need to stub in the variables):
 <PATH_TO_LLVM_SRC>/clang-tools-extra/clang-tidy/tool/run-clang-tidy.py \
@@ -235,12 +235,12 @@ Copy-Paste Friendly (though you'll still need to stub in the variables):
     -checks=<CHECKS> \
     -header-filter=<FILTER> \
     -fix \
-    chrome/browser
+    'chrome/browser/.*'
 ```
 
-\*It's not clear which, if any, `gn` flags may cause issues for
-`clang-tidy`. I've had no problems building a component release build,
-both with and without goma. if you run into issues, let us know!
+Note that the source file regex must match how the build specified the file.
+This means that on Windows, you must use (escaped) backslashes even from a bash
+shell.
 
 ### Questions
 

ui/views/.clang-tidy

 ---
-Checks: '-*,
-         google-build-namespaces,
-         google-explicit-constructor,
-         google-readability-casting,
-         google-readability-namespace-comments,
-         modernize-avoid-bind,
-         modernize-loop-convert,
-         modernize-make-shared,
-         modernize-make-unique,
-         modernize-redundant-void-arg,
-         modernize-replace-auto-ptr,
-         modernize-replace-random-shuffle,
-         modernize-shrink-to-fit,
-         modernize-use-bool-literals,
-         modernize-use-default-member-init,
-         modernize-use-emplace,
-         modernize-use-equals-default,
-         modernize-use-noexcept,
-         modernize-use-nullptr,
-         modernize-use-override,
-         modernize-use-transparent-functors,
-         modernize-use-using,
-         readability-redundant-member-init'
-HeaderFilterRegex: 'ui/views/*'
-CheckOptions:
-  - key: modernize-use-default-member-init.UseAssignment
-    value: 1
+  Checks:          'google-build-namespaces,
+                    google-readability-namespace-comments,
+                    modernize-replace-auto-ptr,
+                    modernize-use-using'
+  HeaderFilterRegex: 'ui/views/*'
 ...