Optimize visualbench offscreen blits

tools/VisualBench/VisualBenchmarkStream.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  */
 
 #include <VisualBench/VisualBenchmarkStream.h>
 #include <VisualBench/WrappedBenchmark.h>
@@ skipping 21 matching lines @@
                "If a bench does not match any list entry,\n"
                "it is skipped unless some list entry starts with ~");
 DEFINE_string(skps, "skps", "Directory to read skps from.");
 
 // We draw a big nonAA path to warmup the gpu / cpu
 #include "SkPerlinNoiseShader.h"
 class WarmupBench : public Benchmark {
 public:
     WarmupBench() {
         sk_tool_utils::make_big_path(fPath);
+        fPerlinRect = SkRect::MakeLTRB(0., 0., 400., 400.);
     }
 private:
     const char* onGetName() override { return "warmupbench"; }
+    SkIPoint onGetSize() override {
+        int w = SkScalarCeilToInt(SkTMax(fPath.getBounds().right(), fPerlinRect.right()));
+        int h = SkScalarCeilToInt(SkTMax(fPath.getBounds().bottom(), fPerlinRect.bottom()));
+        return SkIPoint::Make(w, h);
+    }
     void onDraw(int loops, SkCanvas* canvas) override {
         // We draw a big path to warm up the cpu, and then use perlin noise shader to warm up the
         // gpu
         SkPaint paint;
         paint.setStyle(SkPaint::kStroke_Style);
         paint.setStrokeWidth(2);
 
         SkPaint perlinPaint;
         perlinPaint.setShader(SkPerlinNoiseShader::CreateTurbulence(0.1f, 0.1f, 1, 0,
                                                                     nullptr))->unref();
-        SkRect rect = SkRect::MakeLTRB(0., 0., 400., 400.);
         for (int i = 0; i < loops; i++) {
             canvas->drawPath(fPath, paint);
-            canvas->drawRect(rect, perlinPaint);
+            canvas->drawRect(fPerlinRect, perlinPaint);
 #if SK_SUPPORT_GPU
             // Ensure the GrContext doesn't batch across draw loops.
             if (GrContext* context = canvas->getGrContext()) {
                 context->flush();
             }
 #endif
         }
     }
     SkPath fPath;
+    SkRect fPerlinRect;
 };
 
 VisualBenchmarkStream::VisualBenchmarkStream(const SkSurfaceProps& surfaceProps)
     : fSurfaceProps(surfaceProps)
     , fBenches(BenchRegistry::Head())
     , fGMs(skiagm::GMRegistry::Head())
     , fSourceType(nullptr)
     , fBenchType(nullptr)
     , fCurrentSKP(0)
     , fIsWarmedUp(false) {
@@ skipping 92 matching lines @@
         }
 
         SkString name = SkOSPath::Basename(path.c_str());
         fSourceType = "skp";
         fBenchType = "playback";
         return new VisualSKPBench(name.c_str(), pic.get());
     }
 
     return nullptr;
 }