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/GrMemoryPoolBench.cpp b/bench/GrMemoryPoolBench.cpp
index d6c4b77..29c0893 100644
--- a/bench/GrMemoryPoolBench.cpp
+++ b/bench/GrMemoryPoolBench.cpp
@@ -46,7 +46,7 @@
         return "grmemorypool_stack";
     }
 
-    virtual void onDraw(SkCanvas* canvas) {
+    virtual void onDraw(SkCanvas*) {
         SkRandom r;
         enum {
             kMaxObjects = 4 * (1 << 10),
@@ -102,7 +102,7 @@
         return "grmemorypool_random";
     }
 
-    virtual void onDraw(SkCanvas* canvas) {
+    virtual void onDraw(SkCanvas*) {
         SkRandom r;
         enum {
             kMaxObjects = 4 * (1 << 10),
@@ -140,7 +140,7 @@
         return "grmemorypool_queue";
     }
 
-    virtual void onDraw(SkCanvas* canvas) {
+    virtual void onDraw(SkCanvas*) {
         SkRandom r;
         A* objects[M];
         for (int i = 0; i < N; i++) {