Remove SkBenchmark::postDraw.

Only one bench used this feature, and it's for things that'd be done by the
destructor anyway.

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

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/329853007
diff --git a/bench/benchmain.cpp b/bench/benchmain.cpp
index 42428b4..af70878 100644
--- a/bench/benchmain.cpp
+++ b/bench/benchmain.cpp
@@ -78,18 +78,6 @@
     const skiagm::GMRegistry* fGMs;
 };
 
-class AutoPrePostDraw {
-public:
-    AutoPrePostDraw(SkBenchmark* bench) : fBench(bench) {
-        fBench->preDraw();
-    }
-    ~AutoPrePostDraw() {
-        fBench->postDraw();
-    }
-private:
-    SkBenchmark* fBench;
-};
-
 static void make_filename(const char name[], SkString* path) {
     path->set(name);
     for (int i = 0; name[i]; i++) {
@@ -462,7 +450,7 @@
         bench->setForceAA(FLAGS_forceAA);
         bench->setForceFilter(FLAGS_forceFilter);
         bench->setDither(dither);
-        AutoPrePostDraw appd(bench);
+        bench->preDraw();
 
         bool loggedBenchName = false;
         for (int i = 0; i < configs.count(); ++i) {