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

src/pipe/SkPipeCanvas.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 "SkPathEffect.h"
 #include "SkColorFilter.h"
 #include "SkDrawLooper.h"
@@ skipping 1018 matching lines @@
 }
 
 void SkPipeSerializer::write(SkPicture* picture, SkWStream* stream) {
     stream->write32(kDefinePicture_ExtPipeVerb);
     SkRect cull = picture->cullRect();
     stream->write(&cull.fLeft, sizeof(SkRect));
     picture->playback(this->beginWrite(cull, stream));
     this->endWrite();
 }
 
+/*
+ *  This either writes
+ *      kDefineImage + image_index [followed by contents]
+ *  or

[mtklein, 2016/09/13 21:24:52]

Might be simpler to think about if it's

if (!defined) {
   kDefinedImage + image_index
}
kWriteImage + image_index

So that you never have to think, sometimes define means define+write, sometimes
just define.

[reed1, 2016/09/13 23:11:34]

Seems like it actually complicates the reader, where today its a simple switch
statement. Do you still prefer this idea after looking at the reader?

[reed1, 2016/09/13 23:36:29]

I've uploaded your suggestion, and the reader is fine.

+ *      kWriteImage + image_index (image_index == 0 means failure)
+ */
 void SkPipeSerializer::write(SkImage* image, SkWStream* stream) {
-    stream->write32(kDefineImage_ExtPipeVerb);
-    SkPipeWriter writer(stream, &fImpl->fDeduper);
-    writer.writeImage(image);
+    int index = fImpl->fDeduper.findImage(image);
+    if (index) {
+        stream->write32(pack_verb(SkPipeVerb::kWriteImage, index));
+    } else {
+        fImpl->fDeduper.setStream(stream);
+        index = fImpl->fDeduper.findOrDefineImage(image);
+        if (0 == index) {
+            // failed to define the image
+            stream->write32(pack_verb(SkPipeVerb::kWriteImage, index));
+        }
+    }
 }
 
 SkCanvas* SkPipeSerializer::beginWrite(const SkRect& cull, SkWStream* stream) {
     SkASSERT(nullptr == fImpl->fCanvas);
     fImpl->fCanvas.reset(new SkPipeCanvas(cull, &fImpl->fDeduper, stream));
     fImpl->fDeduper.setStream(stream);
     fImpl->fDeduper.setCanvas(fImpl->fCanvas.get());
     return fImpl->fCanvas.get();
 }
 
 void SkPipeSerializer::endWrite() {
     fImpl->fCanvas->restoreToCount(1);
     fImpl->fCanvas.reset(nullptr);
+    fImpl->fDeduper.setCanvas(nullptr);
 }