Bench : Unused parameters cleanup

I removed unused parameters in bench wherever it was trivial to do so.
Review URL: https://codereview.appspot.com/7411046

git-svn-id: http://skia.googlecode.com/svn/trunk@7988 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/bench/MatrixBench.cpp b/bench/MatrixBench.cpp
index f739715..d1a7dd2 100644
--- a/bench/MatrixBench.cpp
+++ b/bench/MatrixBench.cpp
@@ -28,7 +28,7 @@
         return fName.c_str();
     }
 
-    virtual void onDraw(SkCanvas* canvas) {
+    virtual void onDraw(SkCanvas*) {
         int n = SkBENCHLOOP(N * this->mulLoopCount());
         for (int i = 0; i < n; i++) {
             this->performTest();