Distinguish common and unique names for skiaperf.com.

Turns out we tack on the size post-facto in ResultsWriter::bench(), so the only
place we need getUniqueName() to differ from getName() is SKPBench.

BUG=skia:
R=jcgregorio@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/552303004
diff --git a/bench/Benchmark.h b/bench/Benchmark.h
index 8e8eeff..508d1da 100644
--- a/bench/Benchmark.h
+++ b/bench/Benchmark.h
@@ -49,6 +49,7 @@
     Benchmark();
 
     const char* getName();
+    const char* getUniqueName();
     SkIPoint getSize();
 
     enum Backend {
@@ -98,6 +99,7 @@
     virtual void setupPaint(SkPaint* paint);
 
     virtual const char* onGetName() = 0;
+    virtual const char* onGetUniqueName() { return this->onGetName(); }
     virtual void onPreDraw() {}
     // Each bench should do its main work in a loop like this:
     //   for (int i = 0; i < loops; i++) { <work here> }