Fix up -Winconsistent-missing-override

  (and a couple presubmit fixes)

This allows us to turn back on -Werror for LLVM coverage builds,
and more generally supports building with Clang 3.7.

No public API changes.
TBR=reed@google.com

BUG=skia:

Review URL: https://codereview.chromium.org/1232463006

1 files changed, 1 insertions, 1 deletions

diff --git a/bench/StrokeBench.cpp b/bench/StrokeBench.cpp
index 8417bbf186..70dc79e45f 100644
--- a/bench/StrokeBench.cpp
+++ b/bench/StrokeBench.cpp
@@ -21,7 +21,7 @@ public:
     }
 
 protected:
-    virtual bool isSuitableFor(Backend backend) {
+    bool isSuitableFor(Backend backend) override {
         return backend == kNonRendering_Backend;
     }