Avoid initializing memory twice on incomplete RLE bmps

src/codec/SkBmpRLECodec.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBmpRLECodec.h"
 #include "SkCodecPriv.h"
 #include "SkColorPriv.h"
@@ skipping 485 matching lines @@
 
 private:
     int onSetSampleX(int sampleX) override {
         return fCodec->setSampleX(sampleX);
     }
 
     // Unowned pointer. fCodec will delete this class in its destructor.
     SkBmpRLECodec* fCodec;
 };
 
-SkSampler* SkBmpRLECodec::getSampler(bool createIfNecessary) {
-    if (!fSampler && createIfNecessary) {
+SkSampler* SkBmpRLECodec::getSampler(bool /*createIfNecessary*/) {
+    // We will always create an SkBmpRLESampler if one is requested.
+    // This allows clients to always use the SkBmpRLESampler's
+    // version of fill(), which does nothing since RLE decodes have
+    // already filled pixel memory.  This seems fine, since creating
+    // an SkBmpRLESampler is pretty inexpensive.
+    if (!fSampler) {
         fSampler.reset(new SkBmpRLESampler(this));
     }
 
     return fSampler;
 }
 
 int SkBmpRLECodec::setSampleX(int sampleX){
     fSampleX = sampleX;
     return get_scaled_dimension(this->getInfo().width(), sampleX);
 }