Update more directories under src/ to follow C++11 style rule for {virtual,override}.

The Google style guide states that only one of {virtual,override,final}
should be used for each declaration, since override implies virtual and
final implies both virtual and override.

The entries were found using the following command line:

$ find src/ -iname "*.h" -o -iname "*.cpp" | xargs pcregrep -M
"[^\n/]+virtual\ [^;{]+\ [a-zA-Z0-9_]+\([^;{]+\ override[ \n]*[;{]"

The regex was a courtesy of nick@chromium.org

BUG=None
R=mtklein@google.com
NOPRESUBMIT=true

Review URL: https://codereview.chromium.org/1086143003
diff --git a/src/image/SkSurface_Raster.cpp b/src/image/SkSurface_Raster.cpp
index 45237b0..28b972b 100644
--- a/src/image/SkSurface_Raster.cpp
+++ b/src/image/SkSurface_Raster.cpp
@@ -25,8 +25,7 @@
     SkCanvas* onNewCanvas() override;
     SkSurface* onNewSurface(const SkImageInfo&) override;
     SkImage* onNewImageSnapshot(Budgeted) override;
-    virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y,
-                        const SkPaint*) override;
+    void onDraw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*) override;
     void onCopyOnWrite(ContentChangeMode) override;
 
 private: