Enable ClangTidy check readability-redundant-smartptr-get.

To my surprise, this even works with homegrown smart pointers (such as
SkTLazy).

https://clang.llvm.org/extra/clang-tidy/checks/readability-redundant-smartptr-get.html

Find and remove redundant calls to smart pointer’s .get() method.

Examples:

  ptr.get()->Foo()  ==>  ptr->Foo()
  *ptr.get()  ==>  *ptr
  *ptr->get()  ==>  **ptr
  if (ptr.get() == nullptr) ... => if (ptr == nullptr) ...

Change-Id: I8ff541e0229656b4d8e875c8053a7e6138302547
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/310976
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/.clang-tidy b/.clang-tidy
index 178f4a5..37e8152 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -16,6 +16,7 @@
     performance-unnecessary-copy-initialization,
     readability-const-return-type,
     readability-redundant-preprocessor,
+    readability-redundant-smartptr-get,
     readability-static-accessed-through-instance
 CheckOptions:
   - key:             llvm-namespace-comment.SpacesBeforeComments