Early reporting of opaqueness by decoders.

third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.cpp

Index: third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.cpp
diff --git a/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.cpp b/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.cpp
index bff97c205e1780f9f60392caac16f80acff9d86d..993b1b6fbb10c24e549eed3e4e70689416661251 100644
--- a/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.cpp
+++ b/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.cpp
@@ -92,7 +92,7 @@ public:
         , m_readOffset(readOffset)
         , m_currentBufferSize(0)
         , m_decodingSizeOnly(false)
-        , m_hasAlpha(false)
+        , m_hasAlpha(true)
 #if USE(QCMSLIB)
         , m_rowBuffer()
 #endif
@@ -170,6 +170,13 @@ PNGImageDecoder::~PNGImageDecoder()
 {
 }
 
+bool PNGImageDecoder::frameHasAlphaAtIndex(size_t index) const
+{
+    if (index == 0 && isAllDataReceived() && m_reader && !m_reader->hasAlpha())
+        return false;
+    return ImageDecoder::frameHasAlphaAtIndex(index);
+}
+
 void PNGImageDecoder::headerAvailable()
 {
     png_structp png = m_reader->pngPtr();