Separate zeroing pixel data from setting alpha

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

Index: third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.cpp
diff --git a/third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.cpp b/third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.cpp
index 734a7b2527bed95be6dc11f960bf2a1024f337ac..c1df73bbdede3312ea968881f8d4876bc1dd6216 100644
--- a/third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.cpp
+++ b/third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.cpp
@@ -124,10 +124,6 @@ bool BMPImageReader::decodeBMP(bool onlySize) {
     }
     m_buffer->zeroFillPixelData();
     m_buffer->setStatus(ImageFrame::FramePartial);
-    // setSize() calls eraseARGB(), which resets the alpha flag, so we force
-    // it back to false here.  We'll set it true below in all cases where
-    // these 0s could actually show through.
-    m_buffer->setHasAlpha(false);
 
     // For BMPs, the frame always fills the entire image.
     m_buffer->setOriginalFrameRect(IntRect(IntPoint(), m_parent->size()));
@@ -824,6 +820,7 @@ BMPImageReader::ProcessingResult BMPImageReader::processNonRLEData(
           m_seenNonZeroAlphaPixel = true;
           if (m_seenZeroAlphaPixel) {
             m_buffer->zeroFillPixelData();
+            m_buffer->setHasAlpha(true);
             m_seenZeroAlphaPixel = false;
           } else if (alpha != 255)
             m_buffer->setHasAlpha(true);