Implemented transparent gradients

src/pdf/SkPDFGraphicState.cpp

Index: src/pdf/SkPDFGraphicState.cpp
diff --git a/src/pdf/SkPDFGraphicState.cpp b/src/pdf/SkPDFGraphicState.cpp
index 9cf21458233f6025807ce0be554a59e5e95b1d1c..ad9578578a93e4734f9e16968e2bb5e2c38ac0af 100644
--- a/src/pdf/SkPDFGraphicState.cpp
+++ b/src/pdf/SkPDFGraphicState.cpp
@@ -138,13 +138,17 @@ SkPDFObject* SkPDFGraphicState::GetInvertFunction() {
 
 // static
 SkPDFGraphicState* SkPDFGraphicState::GetSMaskGraphicState(
-        SkPDFFormXObject* sMask, bool invert) {
+        SkPDFFormXObject* sMask, bool invert, bool alpha) {
     // The practical chances of using the same mask more than once are unlikely
     // enough that it's not worth canonicalizing.
     SkAutoMutexAcquire lock(CanonicalPaintsMutex());
 
     SkAutoTUnref<SkPDFDict> sMaskDict(new SkPDFDict("Mask"));
-    sMaskDict->insertName("S", "Alpha");
+    if (alpha) {
+        sMaskDict->insertName("S", "Alpha");
+    } else {
+        sMaskDict->insertName("S", "Luminosity");
+    }
     sMaskDict->insert("G", new SkPDFObjRef(sMask))->unref();
 
     SkPDFGraphicState* result = new SkPDFGraphicState;
@@ -203,6 +207,8 @@ void SkPDFGraphicState::populateDict() {
         fPopulated = true;
         insertName("Type", "ExtGState");
 
+        // do a SMask if paint involves a gradient alpha

[vandebo (ex-Chrome), 2013/07/03 17:07:01]

How would paint involve a gradient alpha?  We have a todo style:
// TODO(uername): Thing to do in full sentence form, referring to a bug if
possible.

[ducky, 2013/07/03 23:32:09]

That wasn't supposed to be there. I somehow missed that going through the
presubmit git diff...

+        //TODO ADD STUFF HERE
         SkAutoTUnref<SkPDFScalar> alpha(
             new SkPDFScalar(SkScalarDiv(fPaint.getAlpha(), 0xFF)));
         insert("CA", alpha.get());