benchmarks: Avoid brackets and commas in test names.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2295483002

Review-Url: https://codereview.chromium.org/2295483002
diff --git a/bench/PatchBench.cpp b/bench/PatchBench.cpp
index 80d5ce0..f029584 100644
--- a/bench/PatchBench.cpp
+++ b/bench/PatchBench.cpp
@@ -101,7 +101,7 @@
         }
         SkString type;
         this->appendName(&type);
-        fName.printf("patch_%s_%s_[%f,%f]", type.c_str(), vertexMode.c_str(),
+        fName.printf("patch_%s_%s_%fx%f", type.c_str(), vertexMode.c_str(),
                     fScale.x(), fScale.y());
         return fName.c_str();
     }