force linking inside of skdiff

Review URL: https://codereview.chromium.org/16879012

git-svn-id: http://skia.googlecode.com/svn/trunk@9669 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tools/skdiff_main.cpp b/tools/skdiff_main.cpp
index a9a1968..9d0bcf5 100644
--- a/tools/skdiff_main.cpp
+++ b/tools/skdiff_main.cpp
@@ -9,6 +9,7 @@
 #include "skdiff_utils.h"
 #include "SkBitmap.h"
 #include "SkData.h"
+#include "SkForceLinking.h"
 #include "SkImageDecoder.h"
 #include "SkImageEncoder.h"
 #include "SkOSFile.h"
@@ -18,6 +19,8 @@
 #include "SkTSearch.h"
 #include "SkTypes.h"
 
+__SK_FORCE_IMAGE_DECODER_LINKING;
+
 /**
  * skdiff
  *