Remove const from `const int loops`.

This drives me nuts, and prevents `while (loops --> 0)`.

BUG=skia:

Review URL: https://codereview.chromium.org/1379923005
diff --git a/bench/GrMemoryPoolBench.cpp b/bench/GrMemoryPoolBench.cpp
index fd29775..3efe653 100644
--- a/bench/GrMemoryPoolBench.cpp
+++ b/bench/GrMemoryPoolBench.cpp
@@ -43,7 +43,7 @@
         return "grmemorypool_stack";
     }
 
-    void onDraw(const int loops, SkCanvas*) override {
+    void onDraw(int loops, SkCanvas*) override {
         SkRandom r;
         enum {
             kMaxObjects = 4 * (1 << 10),
@@ -105,7 +105,7 @@
         return "grmemorypool_random";
     }
 
-    void onDraw(const int loops, SkCanvas*) override {
+    void onDraw(int loops, SkCanvas*) override {
         SkRandom r;
         enum {
             kMaxObjects = 4 * (1 << 10),
@@ -153,7 +153,7 @@
         return "grmemorypool_queue";
     }
 
-    void onDraw(const int loops, SkCanvas*) override {
+    void onDraw(int loops, SkCanvas*) override {
         SkRandom r;
         C* objects[M];
         for (int i = 0; i < loops; i++) {