make allocPixels throw on failure

src/images/SkDecodingImageGenerator.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 "SkData.h"
 #include "SkDecodingImageGenerator.h"
 #include "SkImageDecoder.h"
@@ skipping 51 matching lines @@
         : fInfo(info)
         , fTarget(target)
         , fRowBytes(rowBytes)
     {}
 
     bool isReady() { return (fTarget != NULL); }
 
     virtual bool allocPixelRef(SkBitmap* bm, SkColorTable* ct) {
         if (NULL == fTarget || !equal_modulo_alpha(fInfo, bm->info())) {
             // Call default allocator.
-            return bm->allocPixels(NULL, ct);
+            return bm->tryAllocPixels(NULL, ct);
         }
 
         // TODO(halcanary): verify that all callers of this function
         // will respect new RowBytes.  Will be moot once rowbytes belongs
         // to PixelRef.
         bm->installPixels(fInfo, fTarget, fRowBytes, ct, NULL, NULL);
 
         fTarget = NULL;  // never alloc same pixels twice!
         return true;
     }
@@ skipping 194 matching lines @@
         SkStreamRewindable* stream,
         const SkDecodingImageGenerator::Options& opts) {
     SkASSERT(stream != NULL);
     SkASSERT(stream->unique());
     if ((stream == NULL) || !stream->unique()) {
         SkSafeUnref(stream);
         return NULL;
     }
     return CreateDecodingImageGenerator(NULL, stream, opts);
 }