Merge 85264 - 2011-04-28 Mike Reed <reed@google.com>

Source/WebCore/platform/graphics/skia/GraphicsContextSkia.cpp

Index: Source/WebCore/platform/graphics/skia/GraphicsContextSkia.cpp
===================================================================
--- Source/WebCore/platform/graphics/skia/GraphicsContextSkia.cpp	(revision 85512)
+++ Source/WebCore/platform/graphics/skia/GraphicsContextSkia.cpp	(working copy)
@@ -1047,6 +1047,7 @@
     double blur = blurFloat;
 
     uint32_t mfFlags = SkBlurMaskFilter::kHighQuality_BlurFlag;
+    SkXfermode::Mode colorMode = SkXfermode::kSrc_Mode;
 
     if (m_state.shadowsIgnoreTransforms)  {
         // Currently only the GraphicsContext associated with the
@@ -1055,6 +1056,12 @@
         // with a CanvasRenderingContext.
         mfFlags |= SkBlurMaskFilter::kIgnoreTransform_BlurFlag;
 
+        // CSS wants us to ignore the original's alpha, but Canvas wants us to
+        // modulate with it. Using shadowsIgnoreTransforms to tell us that we're
+        // in a Canvas, we change the colormode to kDst_Mode, so we don't overwrite
+        // it with our layer's (default opaque-black) color.
+        colorMode = SkXfermode::kDst_Mode;
+
         // CG uses natural orientation for Y axis, but the HTML5 canvas spec
         // does not.
         // So we now flip the height since it was flipped in
@@ -1082,7 +1089,7 @@
 
     info.fPaintBits |= SkLayerDrawLooper::kMaskFilter_Bit; // our blur
     info.fPaintBits |= SkLayerDrawLooper::kColorFilter_Bit;
-    info.fColorMode = SkXfermode::kDst_Mode;
+    info.fColorMode = colorMode;
     info.fOffset.set(width, height);
     info.fPostTranslate = m_state.shadowsIgnoreTransforms;