Add support for serializing/deserializing of SkDrawable

src/core/SkReadBuffer.h

Index: src/core/SkReadBuffer.h
diff --git a/src/core/SkReadBuffer.h b/src/core/SkReadBuffer.h
index 48edcfe7620e1018e940b68ac17e73724d85f35a..babd276dad0002f8f26262c8debb14b30adb8370 100644
--- a/src/core/SkReadBuffer.h
+++ b/src/core/SkReadBuffer.h
@@ -22,6 +22,7 @@
 #include "SkReader32.h"
 #include "SkRefCnt.h"
 #include "SkShader.h"
+#include "SkTHash.h"
 #include "SkWriteBuffer.h"
 #include "SkXfermode.h"
 
@@ -202,6 +203,15 @@ public:
     }
 
     /**
+     *  For an input flattenable (specified by name), set custom factory proc
+     *  to use when unflattening.
+     */
+    void setCustomFactory(const char* name, SkFlattenable::Factory factory) {
+        SkFlattenable::Factory defaultFactory = SkFlattenable::NameToFactory(name);
+        fCustomFactory->set(defaultFactory, factory);
+    }
+
+    /**
      *  Provide a function to decode an SkBitmap from encoded data. Only used if the writer
      *  encoded the SkBitmap. If the proper decoder cannot be used, a red bitmap with the
      *  appropriate size will be used.
@@ -218,6 +228,14 @@ public:
 protected:
     SkReader32 fReader;
 
+    /**
+     *  Checks if a custom factory has been set for a given flattenable.
+     *  Returns the custom factory if it exists, or nullptr otherwise.
+     */
+    SkFlattenable::Factory* getCustomFactory(SkFlattenable::Factory factory) {
+        return fCustomFactory->find(factory);
+    }
+
 private:
     bool readArray(void* value, size_t size, size_t elementSize);
 
@@ -233,6 +251,10 @@ private:
     SkFlattenable::Factory* fFactoryArray;
     int                     fFactoryCount;
 
+    // Maps the default Factory to any custom Factory that was specified for
+    // this SkReadBuffer.
+    SkAutoTDelete<SkTHashMap<SkFlattenable::Factory, SkFlattenable::Factory>> fCustomFactory;
+
     SkPicture::InstallPixelRefProc fBitmapDecoder;
 
 #ifdef DEBUG_NON_DETERMINISTIC_ASSERT