Reland Properly set alpha type in webp decode.

src/images/SkImageDecoder_libwebp.cpp

Index: src/images/SkImageDecoder_libwebp.cpp
diff --git a/src/images/SkImageDecoder_libwebp.cpp b/src/images/SkImageDecoder_libwebp.cpp
index 517480665366dfa78231983e087b9a5ef8d728e6..4e23e50f5760fcf2024799265d7b4257823cf071 100644
--- a/src/images/SkImageDecoder_libwebp.cpp
+++ b/src/images/SkImageDecoder_libwebp.cpp
@@ -298,8 +298,20 @@ bool SkWEBPImageDecoder::setDecodeConfig(SkBitmap* decodedBitmap,
         return false;
     }
 
-    return decodedBitmap->setConfig(config, width, height, 0,
-                                    fHasAlpha ? kPremul_SkAlphaType : kOpaque_SkAlphaType);
+    SkImageInfo info;
+    info.fWidth = width;
+    info.fHeight = height;
+    info.fColorType = SkBitmapConfigToColorType(config);
+    if (SkToBool(fHasAlpha)) {
+        if (this->getRequireUnpremultipliedColors()) {
+            info.fAlphaType = kUnpremul_SkAlphaType;
+        } else {
+            info.fAlphaType = kPremul_SkAlphaType;
+        }
+    } else {
+        info.fAlphaType = kOpaque_SkAlphaType;
+    }
+    return decodedBitmap->setConfig(info);
 }
 
 bool SkWEBPImageDecoder::onBuildTileIndex(SkStreamRewindable* stream,