Support lossy and lossless <canvas>.toDataURL for webp

Source/platform/MIMETypeRegistry.cpp

Index: Source/platform/MIMETypeRegistry.cpp
diff --git a/Source/platform/MIMETypeRegistry.cpp b/Source/platform/MIMETypeRegistry.cpp
index 8887aeddc4f47e91c5b8a8d0af1e715051aa0f8c..c845be05c0289a892526e077fc38dd188cb24ffe 100644
--- a/Source/platform/MIMETypeRegistry.cpp
+++ b/Source/platform/MIMETypeRegistry.cpp
@@ -87,7 +87,7 @@ bool MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(const String& mimeTyp
 {
     if (equalIgnoringCase(mimeType, "image/jpeg") || equalIgnoringCase(mimeType, "image/png"))
         return true;
-    if (equalIgnoringCase(mimeType, "image/webp"))
+    if (equalIgnoringCase(mimeType, "image/webp") || equalIgnoringCase(mimeType, "image/webplossless"))
         return true;
     return false;
 }