Fixing valgrind error

src/effects/SkBitmapSource.cpp

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapSource.h"
 #include "SkDevice.h"
 #include "SkCanvas.h"
@@ skipping 13 matching lines @@
     fBitmap(bitmap),
     fSrcRect(srcRect),
     fDstRect(dstRect) {
 }
 
 SkBitmapSource::SkBitmapSource(SkFlattenableReadBuffer& buffer)
   : INHERITED(0, buffer) {
     fBitmap.unflatten(buffer);
     buffer.readRect(&fSrcRect);
     buffer.readRect(&fDstRect);
-    buffer.validate(SkIsValidRect(fSrcRect) && SkIsValidRect(fDstRect));
+    buffer.validate(buffer.isValid() && SkIsValidRect(fSrcRect) && SkIsValidRect(fDstRect));
 }
 
 void SkBitmapSource::flatten(SkFlattenableWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     fBitmap.flatten(buffer);
     buffer.writeRect(fSrcRect);
     buffer.writeRect(fDstRect);
 }
 
 bool SkBitmapSource::onFilterImage(Proxy* proxy, const SkBitmap&, const SkMatrix& matrix,
@@ skipping 25 matching lines @@
     paint.setFilterLevel(
         fSrcRect.width() == dstRect.width() && fSrcRect.height() == dstRect.height() ?
         SkPaint::kNone_FilterLevel : SkPaint::kMedium_FilterLevel);
     canvas.drawBitmapRectToRect(fBitmap, &fSrcRect, dstRect, &paint);
 
     *result = device.get()->accessBitmap(false);
     offset->fX += dstIRect.fLeft;
     offset->fY += dstIRect.fTop;
     return true;
 }