Mark overridden destructors with 'override' and remove 'virtual'

This silences a new warning in clang 5.0

Change-Id: Ieb5b75a6ffed60107c3fd16075d2ecfd515b55e8
Reviewed-on: https://skia-review.googlesource.com/10006
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
diff --git a/samplecode/SamplePathText.cpp b/samplecode/SamplePathText.cpp
index 26ffb9a..bb2142e 100644
--- a/samplecode/SamplePathText.cpp
+++ b/samplecode/SamplePathText.cpp
@@ -116,7 +116,7 @@
         , fBackMatrices(kNumPaths) {
     }
 
-    ~MovingPathText() {
+    ~MovingPathText() override {
         fBackgroundAnimationTask.wait();
     }
 
@@ -227,7 +227,7 @@
         : fFrontPaths(kNumPaths)
         , fBackPaths(kNumPaths) {}
 
-    ~WavyPathText() {
+    ~WavyPathText() override {
         fBackgroundAnimationTask.wait();
     }