SkPDF: simplify drawImage/Bitmap/Sprite code.

  - SkImageSubset becomes SkKeyedImage
  - SkPDFCanvas::onDraw{Bitmap, Image} go away
  - Remove SkPDFCanvas: base classes now do the right thing.
  - SkPDFDevice::draw{Bitmap,Image}{Rect,}() simplified
  - 244 fewer SLOC.

All but a few PDFs are identical, those rasterize almost the same.

Change-Id: I3ceb3b8935c689719cedf1ad544b0407b5c1733e
Reviewed-on: https://skia-review.googlesource.com/22218
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
diff --git a/src/pdf/SkKeyedImage.cpp b/src/pdf/SkKeyedImage.cpp
new file mode 100644
index 0000000..bf19632
--- /dev/null
+++ b/src/pdf/SkKeyedImage.cpp
@@ -0,0 +1,45 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkKeyedImage.h"
+
+#include "SkImage_Base.h"
+
+SkKeyedImage::SkKeyedImage(sk_sp<SkImage> i) : fImage(std::move(i)) {
+    if (fImage) {
+        if (const SkBitmap* bm = as_IB(fImage.get())->onPeekBitmap()) {
+            SkIPoint o = bm->pixelRefOrigin();
+            fKey = {fImage->bounds().makeOffset(o.fX, o.fY), bm->getGenerationID()};
+        } else {
+            fKey = {fImage->bounds(), fImage->uniqueID()};
+        }
+    }
+}
+
+SkKeyedImage::SkKeyedImage(const SkBitmap& bm) : fImage(SkImage::MakeFromBitmap(bm)) {
+    if (fImage) {
+        fKey = {bm.getSubset(), bm.getGenerationID()};
+    }
+}
+
+SkKeyedImage SkKeyedImage::subset(SkIRect subset) const {
+    SkKeyedImage img;
+    if (fImage && subset.intersect(fImage->bounds())) {
+        img.fImage = fImage->makeSubset(subset);
+        if (img.fImage) {
+            img.fKey = {subset.makeOffset(fKey.fSubset.x(), fKey.fSubset.y()), fKey.fID};
+        }
+    }
+    return img;
+}
+
+sk_sp<SkImage> SkKeyedImage::release() {
+    sk_sp<SkImage> image = std::move(fImage);
+    SkASSERT(nullptr == fImage);
+    fKey = {{0, 0, 0, 0}, 0};
+    return image;
+}