Fix iOS build.

src/images/SkForceLinking.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 "SkForceLinking.h"
 #include "SkImageDecoder.h"
 
 // This method is required to fool the linker into not discarding the pre-main
 // initialization and registration of the decoder classes. Passing true will
 // cause memory leaks.
 int SkForceLinking(bool doNotPassTrue) {
     if (doNotPassTrue) {
         SkASSERT(false);
         CreateJPEGImageDecoder();
         CreateWEBPImageDecoder();
         CreateBMPImageDecoder();
         CreateICOImageDecoder();
         CreateWBMPImageDecoder();
         // Only link GIF and PNG on platforms that build them. See images.gyp
-#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN) && !defined(SK_BUILD_FOR_NACL)
+#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN) && !defined(SK_BUILD_FOR_NACL) \
+        && !defined(SK_BUILD_FOR_IOS)
         CreateGIFImageDecoder();
 #endif
-#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN)
+#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN) && !defined(SK_BUILD_FOR_IOS)
         CreatePNGImageDecoder();
 #endif
         return -1;
     }
     return 0;
 }