Support lossy and lossless <canvas>.toDataURL for webp

Source/platform/graphics/ImageBuffer.cpp

 /*
  * Copyright (c) 2008, Google Inc. All rights reserved.
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
@@ skipping 333 matching lines @@
 static bool encodeImage(const ImageDataBuffer& source, const String& mimeType, const double* quality, Vector<char>* output)
 {
     Vector<unsigned char>* encodedImage = reinterpret_cast<Vector<unsigned char>*>(output);
 
     if (mimeType == "image/jpeg") {
         int compressionQuality = JPEGImageEncoder::DefaultCompressionQuality;
         if (quality && *quality >= 0.0 && *quality <= 1.0)
             compressionQuality = static_cast<int>(*quality * 100 + 0.5);
         if (!JPEGImageEncoder::encode(source, compressionQuality, encodedImage))
             return false;
+    } else if (mimeType == "image/webplossless") {
+        int compressionQuality = WEBPImageEncoder::DefaultCompressionQuality;
+        if (quality && *quality >= 0.0 && *quality <= 1.0)
+            compressionQuality = static_cast<int>(*quality * 100 + 0.5);
+        if (!WEBPImageEncoder::encode(source, compressionQuality, encodedImage, WEBPImageEncoder::Lossless))
+            return false;
     } else if (mimeType == "image/webp") {
         int compressionQuality = WEBPImageEncoder::DefaultCompressionQuality;
         if (quality && *quality >= 0.0 && *quality <= 1.0)
             compressionQuality = static_cast<int>(*quality * 100 + 0.5);
         if (!WEBPImageEncoder::encode(source, compressionQuality, encodedImage))
             return false;
     } else {
         if (!PNGImageEncoder::encode(source, encodedImage))
             return false;
         ASSERT(mimeType == "image/png");
     }
 
     return true;
 }
 
 String ImageDataBuffer::toDataURL(const String& mimeType, const double* quality) const
 {
     ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));
 
     Vector<char> encodedImage;
     if (!encodeImage(*this, mimeType, quality, &encodedImage))
         return "data:,";
 
-    return "data:" + mimeType + ";base64," + base64Encode(encodedImage);
+    // webplossless is an encoder selector: map it to the actual mimeType "image/webp".
+

[acterhd, 2015/08/27 17:18:19]

I'm used ternary operator for replace mimes. 

+    String encodedImageMimeType = mimeType;
+    if (mimeType == "image/webplossless")
+        encodedImageMimeType = String("image/webp");
+
+    return "data:" + encodedImageMimeType + ";base64," + base64Encode(encodedImage);
 }
 
 } // namespace blink