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 1592e40551fb7159220dfa533ae47e859cc92485..4e52222c46a9913062d5e67a78570eebe35e087b 100644
--- a/src/pdf/SkPDFDevice.cpp
+++ b/src/pdf/SkPDFDevice.cpp
@@ -1419,7 +1419,8 @@ 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,
@@ -1575,12 +1576,16 @@ 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()),