Remove (almost) unused read/writeFunctionPtr API.

src/core/SkValidatingReadBuffer.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkErrorInternals.h"
 #include "SkValidatingReadBuffer.h"
@@ skipping 263 matching lines @@
     size_t offset = fReader.offset();
     obj = (*factory)(*this);
     // check that we read the amount we expected
     size_t sizeRead = fReader.offset() - offset;
     this->validate(sizeRecorded == sizeRead);
     if (fError) {
         obj = nullptr;
     }
     return obj.release();
 }
-
-void SkValidatingReadBuffer::skipFlattenable() {
-    SkString name;
-    this->readString(&name);
-    if (fError) {
-        return;
-    }
-    uint32_t sizeRecorded = this->readUInt();
-    this->skip(sizeRecorded);
-}