Fix the build.

Remove an unused function warning.

Review URL: https://codereview.chromium.org/14785008

git-svn-id: http://skia.googlecode.com/svn/trunk@8942 2bbb7eff-a529-9590-31e7-b0007b416f81

src/images/SkImageDecoder.cpp

@@ -348,6 +348,7 @@ namespace {
      *  Make sure to keep it in sync with images.gyp, so only the encoders
      *  which are created on a platform are linked.
      */
+    void force_linking();
     void force_linking() {
         SkASSERT(false);
         CreateJPEGImageDecoder();