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/src/shaders/SkPerlinNoiseShader.cpp b/src/shaders/SkPerlinNoiseShader.cpp
index c16d99f..098f781 100644
--- a/src/shaders/SkPerlinNoiseShader.cpp
+++ b/src/shaders/SkPerlinNoiseShader.cpp
@@ -760,8 +760,7 @@
         return new GrGLPerlinNoise;
     }
 
-    virtual void onGetGLSLProcessorKey(const GrShaderCaps& caps,
-                                       GrProcessorKeyBuilder* b) const override {
+    void onGetGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override {
         GrGLPerlinNoise::GenKey(*this, caps, b);
     }