make allocPixels throw on failure

src/images/SkImageDecoder_libwebp.cpp

 /*
  * Copyright 2010, The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
@@ skipping 357 matching lines @@
         bitmap = &tmpBitmap;
     }
 
     if (bitmap->isNull()) {
         if (!setDecodeConfig(bitmap, width, height)) {
             return false;
         }
         // alloc from native heap if it is a temp bitmap. (prevent GC)
         bool allocResult = (bitmap == decodedBitmap)
                                ? allocPixelRef(bitmap, NULL)
-                               : bitmap->allocPixels();
+                               : bitmap->tryAllocPixels();
         if (!allocResult) {
             return return_false(*decodedBitmap, "allocPixelRef");
         }
 #ifdef SK_SUPPORT_LEGACY_IMAGEDECODER_CHOOSER
     } else {
         // This is also called in setDecodeConfig in above block.
         // i.e., when bitmap->isNull() is true.
         if (!chooseFromOneChoice(bitmap->colorType(), width, height)) {
             return false;
         }
@@ skipping 288 matching lines @@
     return SkImageDecoder::kUnknown_Format;
 }
 
 static SkImageEncoder* sk_libwebp_efactory(SkImageEncoder::Type t) {
       return (SkImageEncoder::kWEBP_Type == t) ? SkNEW(SkWEBPImageEncoder) : NULL;
 }
 
 static SkImageDecoder_DecodeReg gDReg(sk_libwebp_dfactory);
 static SkImageDecoder_FormatReg gFormatReg(get_format_webp);
 static SkImageEncoder_EncodeReg gEReg(sk_libwebp_efactory);