Force linking with image decoders for images project.

src/images/SkImageDecoder.cpp

Index: src/images/SkImageDecoder.cpp
diff --git a/src/images/SkImageDecoder.cpp b/src/images/SkImageDecoder.cpp
index 16cba641db4bade629f2ce5be63a779b41930c64..2c3edc8be5328313ecf9f4dcf191cdbdbb7cb691 100644
--- a/src/images/SkImageDecoder.cpp
+++ b/src/images/SkImageDecoder.cpp
@@ -339,3 +339,28 @@ bool SkImageDecoder::DecodeStream(SkStream* stream, SkBitmap* bm,
     }
     return success;
 }
+
+namespace {
+    /**
+     *  This function leaks, but that is okay because it is not intended
+     *  to be called. It is only here so that the linker will include the
+     *  decoders.
+     *  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() {
+        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)
+        CreateGIFImageDecoder();
+#endif
+#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN)
+        CreatePNGImageDecoder();
+#endif
+    }
+}