Revert of Canvas.toDataURL to use SkBitmap::readPixels to avoid uninitialized memory

Source/platform/graphics/ImageBuffer.cpp

Index: Source/platform/graphics/ImageBuffer.cpp
diff --git a/Source/platform/graphics/ImageBuffer.cpp b/Source/platform/graphics/ImageBuffer.cpp
index 74213e280821408ec7c084866bed333880c71649..7c1c32943be7f9626c45a5dd80d243c317fae131 100644
--- a/Source/platform/graphics/ImageBuffer.cpp
+++ b/Source/platform/graphics/ImageBuffer.cpp
@@ -317,7 +317,8 @@
     canvas()->writePixels(info, srcAddr, srcBytesPerRow, destX, destY);
 }
 
-static bool encodeImage(const ImageDataBuffer& source, const String& mimeType, const double* quality, Vector<char>* output)
+template <typename T>
+static bool encodeImage(T& source, const String& mimeType, const double* quality, Vector<char>* output)
 {
     Vector<unsigned char>* encodedImage = reinterpret_cast<Vector<unsigned char>*>(output);
 
@@ -342,6 +343,17 @@
     return true;
 }
 
+String ImageBuffer::toDataURL(const String& mimeType, const double* quality) const
+{
+    ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));
+
+    Vector<char> encodedImage;
+    if (!isSurfaceValid() || !encodeImage(m_surface->bitmap(), mimeType, quality, &encodedImage))
+        return "data:,";
+
+    return "data:" + mimeType + ";base64," + base64Encode(encodedImage);
+}
+
 String ImageDataBuffer::toDataURL(const String& mimeType, const double* quality) const
 {
     ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));