Add support for serializing/deserializing of SkDrawable

src/core/SkPictureData.h

Index: src/core/SkPictureData.h
diff --git a/src/core/SkPictureData.h b/src/core/SkPictureData.h
index dbb117ef14456d59470a8bf51df7915a071eb20a..4870305de48f1e009bdcbb63331e7a2e4e241999 100644
--- a/src/core/SkPictureData.h
+++ b/src/core/SkPictureData.h
@@ -9,6 +9,7 @@
 #define SkPictureData_DEFINED
 
 #include "SkBitmap.h"
+#include "SkDrawable.h"
 #include "SkPicture.h"
 #include "SkPictureContentInfo.h"
 #include "SkPictureFlat.h"
@@ -43,6 +44,7 @@ struct SkPictInfo {
 #define SK_PICT_FACTORY_TAG    SkSetFourByteTag('f', 'a', 'c', 't')
 #define SK_PICT_TYPEFACE_TAG   SkSetFourByteTag('t', 'p', 'f', 'c')
 #define SK_PICT_PICTURE_TAG    SkSetFourByteTag('p', 'c', 't', 'r')
+#define SK_PICT_DRAWABLE_TAG   SkSetFourByteTag('d', 'r', 'a', 'w')
 
 // This tag specifies the size of the ReadBuffer, needed for the following tags
 #define SK_PICT_BUFFER_SIZE_TAG     SkSetFourByteTag('a', 'r', 'a', 'y')
@@ -107,6 +109,12 @@ public:
         return reader->validateIndex(index, fPictureCount) ? fPictureRefs[index] : nullptr;
     }
 
+    SkDrawable* getDrawable(SkReadBuffer* reader) const {
+        int index = reader->readInt();
+        SkASSERT(index > 0 && index <= fDrawableCount);
+        return fDrawableRefs[index - 1];
+    }
+
     const SkPaint* getPaint(SkReadBuffer* reader) const {
         const int index = reader->readInt() - 1;
         return reader->validateIndex(index, fPaints.count()) ? &fPaints[index] : nullptr;
@@ -160,6 +168,8 @@ private:
 
     const SkPicture** fPictureRefs;
     int fPictureCount;
+    SkDrawable** fDrawableRefs;
+    int fDrawableCount;
     const SkTextBlob** fTextBlobRefs;
     int fTextBlobCount;
     const SkImage** fImageRefs;