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/tests/ProgramsTest.cpp b/tests/ProgramsTest.cpp
index 35184af..62b32b8 100644
--- a/tests/ProgramsTest.cpp
+++ b/tests/ProgramsTest.cpp
@@ -78,8 +78,7 @@
 
 private:
     BigKeyProcessor() : INHERITED(kBigKeyProcessor_ClassID, kNone_OptimizationFlags) { }
-    virtual void onGetGLSLProcessorKey(const GrShaderCaps& caps,
-                                       GrProcessorKeyBuilder* b) const override {
+    void onGetGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override {
         GLBigKeyProcessor::GenKey(*this, caps, b);
     }
     bool onIsEqual(const GrFragmentProcessor&) const override { return true; }