Don't decode AND mask for an icon that already has alpha information

Source/platform/image-decoders/bmp/BMPImageReader.cpp

Index: Source/platform/image-decoders/bmp/BMPImageReader.cpp
diff --git a/Source/platform/image-decoders/bmp/BMPImageReader.cpp b/Source/platform/image-decoders/bmp/BMPImageReader.cpp
index 55e8190084b1ebdd343c30afae46f2419cfdb18c..d4bc7a6f72d46b04eb26683667e0fa2129de7e19 100644
--- a/Source/platform/image-decoders/bmp/BMPImageReader.cpp
+++ b/Source/platform/image-decoders/bmp/BMPImageReader.cpp
@@ -138,7 +138,7 @@ bool BMPImageReader::decodeBMP(bool onlySize)
 
     // If the image has an AND mask and there was no alpha data, process the
     // mask.
-    if (m_isInICO && !m_decodingAndMask && !m_buffer->hasAlpha()) {
+    if (m_isInICO && !m_decodingAndMask && (!m_bitMasks[3] || !m_seenNonZeroAlphaPixel)) {
         // Reset decoding coordinates to start of image.
         m_coord.setX(0);
         m_coord.setY(m_isTopDown ? 0 : (m_parent->size().height() - 1));