Implemented transparent gradients

src/pdf/SkPDFDevice.cpp

Index: src/pdf/SkPDFDevice.cpp
diff --git a/src/pdf/SkPDFDevice.cpp b/src/pdf/SkPDFDevice.cpp
index 59a8028a76209151e249c35827506346ea68ef87..e00602cc053d184c6b37d68c2059507d22c486a5 100644
--- a/src/pdf/SkPDFDevice.cpp
+++ b/src/pdf/SkPDFDevice.cpp
@@ -1415,7 +1415,8 @@ void SkPDFDevice::drawFormXObjectWithClip(SkPDFFormXObject* xobject,
     this->drawPaint(draw, stockPaint);
     SkAutoTUnref<SkPDFFormXObject> maskFormXObject(createFormXObjectFromDevice());
     SkAutoTUnref<SkPDFGraphicState> sMaskGS(
-        SkPDFGraphicState::GetSMaskGraphicState(maskFormXObject, invertClip));
+        SkPDFGraphicState::GetSMaskGraphicState(maskFormXObject, invertClip,
+                                                SkPDFGraphicState::kAlpha_SMaskMode));
 
     // Draw the xobject with the clip as a mask.
     ScopedContentEntry content(this, &fExistingClipStack, fExistingClipRegion,
@@ -1571,12 +1572,16 @@ void SkPDFDevice::finishContentEntry(const SkXfermode::Mode xfermode,
     if (xfermode == SkXfermode::kSrcIn_Mode ||
             xfermode == SkXfermode::kSrcOut_Mode) {
         sMaskGS.reset(SkPDFGraphicState::GetSMaskGraphicState(
-                dst, xfermode == SkXfermode::kSrcOut_Mode));
+                dst,
+                xfermode == SkXfermode::kSrcOut_Mode,
+                SkPDFGraphicState::kAlpha_SMaskMode));
         fXObjectResources.push(srcFormXObject.get());
         srcFormXObject.get()->ref();
     } else {
         sMaskGS.reset(SkPDFGraphicState::GetSMaskGraphicState(
-                srcFormXObject.get(), xfermode == SkXfermode::kDstOut_Mode));
+                srcFormXObject.get(),
+                xfermode == SkXfermode::kDstOut_Mode,
+                SkPDFGraphicState::kAlpha_SMaskMode));
         // dst already added to fXObjectResources in drawFormXObjectWithClip.
     }
     SkPDFUtils::ApplyGraphicState(addGraphicStateResource(sMaskGS.get()),