add tests/bench for dynamicwstream

BUG=skia:

Change-Id: I5a995b63b1a2975cce8101717777eaa6fc12af21
Reviewed-on: https://skia-review.googlesource.com/6035
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>

bench/StreamBench.cpp

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Benchmark.h"
+#include "SkStream.h"
+
+class StreamBench : public Benchmark {
+    SkString fName;
+public:
+    StreamBench()  {
+        fName.printf("wstream");
+    }
+
+    bool isSuitableFor(Backend backend) override {
+        return backend == kNonRendering_Backend;
+    }
+
+protected:
+    const char* onGetName() override { return fName.c_str(); }
+
+    void onDraw(int loops, SkCanvas* canvas) override {
+        for (int i = 0; i < loops*100; ++i) {
+            SkDynamicMemoryWStream stream;
+            for (int j = 0; j < 100000; ++j) {
+                stream.write32(j);
+                stream.write32(j+j);
+            }
+        }
+    }
+
+private:
+    typedef Benchmark INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+DEF_BENCH(return new StreamBench;)

gn/bench.gni

@@ -111,6 +111,7 @@ bench_sources = [
   "$_bench/SKPAnimationBench.cpp",
   "$_bench/SKPBench.cpp",
   "$_bench/SkRasterPipelineBench.cpp",
+  "$_bench/StreamBench.cpp",
   "$_bench/SortBench.cpp",
   "$_bench/StrokeBench.cpp",
   "$_bench/SwizzleBench.cpp",

tests/StreamTest.cpp

@@ -352,6 +352,7 @@ DEF_TEST(StreamPeek_BlockMemoryStream, rep) {
     SkRandom rand(kSeed << 1);
     uint8_t buffer[4096];
     SkDynamicMemoryWStream dynamicMemoryWStream;
+    size_t totalWritten = 0;
     for (int i = 0; i < 32; ++i) {
         // Randomize the length of the blocks.
         size_t size = rand.nextRangeU(1, sizeof(buffer));
@@ -359,6 +360,8 @@ DEF_TEST(StreamPeek_BlockMemoryStream, rep) {
             buffer[j] = valueSource.nextU() & 0xFF;
         }
         dynamicMemoryWStream.write(buffer, size);
+        totalWritten += size;
+        REPORTER_ASSERT(rep, totalWritten == dynamicMemoryWStream.bytesWritten());
     }
     std::unique_ptr<SkStreamAsset> asset(dynamicMemoryWStream.detachAsStream());
     sk_sp<SkData> expected(SkData::MakeUninitialized(asset->getLength()));