Enable ClangTidy flag modernize-use-override.

https://clang.llvm.org/extra/clang-tidy/checks/modernize-use-override.html

Adds override (introduced in C++11) to overridden virtual functions and
removes virtual from those functions as it is not required.

virtual on non base class implementations was used to help indicate to
the user that a function was virtual. C++ compilers did not use the
presence of this to signify an overridden function.

Change-Id: If66d8919358f72a4035190caf8d7569268037a9a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/310160
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/samplecode/SampleAAGeometry.cpp b/samplecode/SampleAAGeometry.cpp
index 3ac60c1..584589f 100644
--- a/samplecode/SampleAAGeometry.cpp
+++ b/samplecode/SampleAAGeometry.cpp
@@ -1519,7 +1519,7 @@
         return -1;
     }
 
-    virtual Sample::Click* onFindClickHandler(SkScalar x, SkScalar y, skui::ModifierKey modi) override {
+    Sample::Click* onFindClickHandler(SkScalar x, SkScalar y, skui::ModifierKey modi) override {
         SkPoint pt = {x, y};
         int ptHit = hittest_pt(pt);
         if (ptHit >= 0) {