Enable flattening/unflattening with custom unflatten procs

src/core/SkReadBuffer.h

Index: src/core/SkReadBuffer.h
diff --git a/src/core/SkReadBuffer.h b/src/core/SkReadBuffer.h
index 7b12194fc03558a70dba98c2b36c4aae2bcf3bbe..195d421f181a0416044a35466f8fb9f8dcc7542d 100644
--- a/src/core/SkReadBuffer.h
+++ b/src/core/SkReadBuffer.h
@@ -194,6 +194,17 @@ public:
     }
 
     /**
+     *  For an input flattenable (specified by name), set a custom factory proc

[reed1, 2016/04/11 15:07:48]

Dox comments:

1. Does the name get copied, or must the caller keep the ptr alive for the life
of this readbuffer (or longer)?
2. Is there a way to remove a factory?
3. What happens if I specify the same name twice? (but possibly w/ different
factories)

nit: const char name[]

[msarett, 2016/04/19 18:03:50]

Done.
I said no.  I don't think this would be hard to support, I just don't see a
reason to yet.
Done.
Changed to const SkString&.

+     *  to use when unflattening.
+     */
+    void setCustomFactory(const char* name, SkFlattenable::Factory factory) {
+        NameFactoryEntry entry;
+        entry.fName = name;
+        entry.fFactory = factory;
+        fCustomFactory.push_back(entry);
+    }
+
+    /**
      *  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.
@@ -210,6 +221,20 @@ 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(const char* name) {
+        for (int i = 0; i < fCustomFactory.count(); i++) {
+            if (!strcmp(fCustomFactory[i].fName, name)) {
+                return fCustomFactory[i].fFactory;
+            }
+        }
+
+        return nullptr;
+    }
+
 private:
     bool readArray(void* value, size_t size, size_t elementSize);
 
@@ -225,6 +250,14 @@ private:
     SkFlattenable::Factory* fFactoryArray;
     int                     fFactoryCount;
 
+    // Maps the flattenable name to a custom factory that should be used to
+    // create the flattenable.
+    struct NameFactoryEntry {
+        const char*            fName;
+        SkFlattenable::Factory fFactory;
+    };
+    SkTArray<NameFactoryEntry> fCustomFactory;
+
     SkPicture::InstallPixelRefProc fBitmapDecoder;
 
 #ifdef DEBUG_NON_DETERMINISTIC_ASSERT