Fix asan build. Duh, don't return a stack address...

bench/MathBench.cpp

Index: bench/MathBench.cpp
diff --git a/bench/MathBench.cpp b/bench/MathBench.cpp
index 260159f3f0ebf58b513f1f16fb53e406130e9f1f..abe04e13d705cd97bb90bfe80a176fc34b0bbe79 100644
--- a/bench/MathBench.cpp
+++ b/bench/MathBench.cpp
@@ -514,15 +514,16 @@ private:
 
 template <typename T>
 class DivModBench : public SkBenchmark {
-    const char* fName;
+    SkString fName;
 public:
-    explicit DivModBench(const char* name) : fName(name) {
+    explicit DivModBench(const char* name) {
+        fName.printf("divmod_%s", name);
         fIsRendering = false;
     }
 
 protected:
     virtual const char* onGetName() {
-        return SkStringPrintf("divmod_%s", fName).c_str();
+        return fName.c_str();
     }
 
     virtual void onDraw(SkCanvas*) {