Add buffer helper to read directly into SkString to avoid extra copying

src/images/SkImageRef_ashmem.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkImageRef_ashmem.h"
 #include "SkImageDecoder.h"
 #include "SkFlattenableBuffers.h"
@@ skipping 205 matching lines @@
     buffer.writeString(getURI());
 }
 
 SkImageRef_ashmem::SkImageRef_ashmem(SkFlattenableReadBuffer& buffer)
         : INHERITED(buffer) {
     fRec.fFD = -1;
     fRec.fAddr = NULL;
     fRec.fSize = 0;
     fRec.fPinned = false;
     fCT = NULL;
-    char* uri = buffer.readString();
-    if (uri) {
-        setURI(uri);
-        sk_free(uri);
-    }
+
+    SkString uri;
+    buffer.readString(&uri);
+    this->setURI(uri);
 }