SkDocument::setDCTEncoder() for old versions of webkit

tests/PDFDocumentTest.cpp

Index: tests/PDFDocumentTest.cpp
diff --git a/tests/PDFDocumentTest.cpp b/tests/PDFDocumentTest.cpp
index 04c3ede6aa4c595ae7ea6799c23e9d26b1f5d90a..c3a5f0e04165846749a4203861ad250396f94dd1 100644
--- a/tests/PDFDocumentTest.cpp
+++ b/tests/PDFDocumentTest.cpp
@@ -6,10 +6,12 @@
  */
 #include "Test.h"
 
+#include "Resources.h"
 #include "SkCanvas.h"
 #include "SkDocument.h"
 #include "SkOSFile.h"
 #include "SkStream.h"
+#include "SkPixelSerializer.h"
 
 static void test_empty(skiatest::Reporter* reporter) {
     SkDynamicMemoryWStream stream;
@@ -110,3 +112,45 @@ DEF_TEST(document_tests, reporter) {
     test_file(reporter);
     test_close(reporter);
 }
+
+namespace {
+class JPEGSerializer final : public SkPixelSerializer {
+    bool onUseEncodedData(const void*, size_t) override { return true; }
+    SkData* onEncode(const SkPixmap& pixmap) override {
+        SkBitmap bm;
+        return bm.installPixels(pixmap.info(),
+                                pixmap.writable_addr(),
+                                pixmap.rowBytes(),
+                                pixmap.ctable(),
+                                nullptr, nullptr)
+            ? SkImageEncoder::EncodeData(bm, SkImageEncoder::kJPEG_Type, 85)
+            : nullptr;
+    }
+};
+}  // namespace
+
+size_t count_bytes(const SkBitmap& bm, bool useDCT) {
+    SkDynamicMemoryWStream stream;
+    SkAutoTUnref<SkDocument> doc;
+    if (useDCT) {
+        SkAutoTUnref<SkPixelSerializer> serializer(new JPEGSerializer);
+        doc.reset(SkDocument::CreatePDF(
+                          &stream, SK_ScalarDefaultRasterDPI, serializer));
+    } else {
+        doc.reset(SkDocument::CreatePDF(&stream));
+    }
+    SkCanvas* canvas = doc->beginPage(64, 64);
+    canvas->drawBitmap(bm, 0, 0);
+    doc->endPage();
+    doc->close();
+    return stream.bytesWritten();
+}
+
+DEF_TEST(document_dct_encoder, r) {
+    REQUIRE_PDF_DOCUMENT(document_dct_encoder, r);
+    SkBitmap bm;
+    if (GetResourceAsBitmap("mandrill_64.png", &bm)) {
+        // Lossy encoding works better on photographs.
+        REPORTER_ASSERT(r, count_bytes(bm, true) < count_bytes(bm, false));
+    }
+}