change write-image to use pipeverbs like everyone else, and add test

tests/PipeTest.cpp

 /*
  * 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 "Resources.h"
 #include "SkCanvas.h"
 #include "SkPipe.h"
@@ skipping 31 matching lines @@
     }
 
     for (int y = 0; y < info.height(); ++y) {
         if (memcmp(pmapA.addr32(0, y), pmapB.addr32(0, y), info.width() * sizeof(SkPMColor))) {
             return false;
         }
     }
     return true;
 }
 
-DEF_TEST(Pipe_image, reporter) {
+DEF_TEST(Pipe_image_draw_first, reporter) {
     sk_sp<SkImage> img = GetResourceAsImage("mandrill_128.png");
     SkASSERT(img.get());
 
     SkPipeSerializer serializer;
     SkPipeDeserializer deserializer;
 
     SkDynamicMemoryWStream stream;
     SkCanvas* wc = serializer.beginWrite(SkRect::MakeWH(100, 100), &stream);
     wc->drawImage(img, 0, 0, nullptr);
     serializer.endWrite();
@@ skipping 16 matching lines @@
     auto img1 = drain_as_image(&deserializer, &stream);
     REPORTER_ASSERT(reporter, deep_equal(img.get(), img1.get()));
 
     // try serializing the same image directly (again), check that it is the same!
     serializer.write(img.get(), &stream);
     size_t offset3 = stream.bytesWritten();
     REPORTER_ASSERT(reporter, offset3 <= 32);
     auto img2 = drain_as_image(&deserializer, &stream);
     REPORTER_ASSERT(reporter, img1.get() == img2.get());
 }
+
+DEF_TEST(Pipe_image_draw_second, reporter) {
+    sk_sp<SkImage> img = GetResourceAsImage("mandrill_128.png");
+    SkASSERT(img.get());
+
+    SkPipeSerializer serializer;
+    SkPipeDeserializer deserializer;
+    SkDynamicMemoryWStream stream;
+
+    serializer.write(img.get(), &stream);
+    size_t offset0 = stream.bytesWritten();
+    REPORTER_ASSERT(reporter, offset0 > 100);   // the raw image must be sorta big
+    drain_as_image(&deserializer, &stream);
+
+    // The 2nd image should be nice and small
+    serializer.write(img.get(), &stream);
+    size_t offset1 = stream.bytesWritten();
+    REPORTER_ASSERT(reporter, offset1 <= 32);
+    drain_as_image(&deserializer, &stream);
+
+    // Now try drawing the image, it should also be small
+    SkCanvas* wc = serializer.beginWrite(SkRect::MakeWH(100, 100), &stream);
+    wc->drawImage(img, 0, 0, nullptr);
+    serializer.endWrite();
+    size_t offset2 = stream.bytesWritten();
+    REPORTER_ASSERT(reporter, offset2 <= 32);
+}