Updates to skimage tool to use it for testing.

src/images/SkImageDecoder_FactoryRegistrar.cpp

 /*
  * Copyright 2013 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
+#include "SkErrorInternals.h"
 #include "SkImageDecoder.h"
 #include "SkStream.h"
 #include "SkTRegistry.h"
 
 // This file is used for registration of SkImageDecoders. It also holds a function
 // for checking all the the registered SkImageDecoders for one that matches an
 // input SkStream.
 
 typedef SkTRegistry<SkImageDecoder*, SkStream*> DecodeReg;
 
@@ skipping 20 matching lines @@
             return NULL;
         }
 
         if (codec) {
             return codec;
         }
         curr = curr->next();
     }
     return NULL;
 }
+
+typedef SkTRegistry<SkImageDecoder::Format, SkStream*> FormatReg;
+
+template FormatReg* SkTRegistry<SkImageDecoder::Format, SkStream*>::gHead;
+
+SkImageDecoder::Format SkImageDecoder::GetFormat(SkStream* stream) {
+    const FormatReg* curr = FormatReg::Head();
+    while (curr != NULL) {
+        Format format = curr->factory()(stream);
+        if (!stream->rewind()) {
+            SkErrorInternals::SetError(kInvalidOperation_SkError,
+                                       "Unable to rewind the image stream\n");
+            return kUnknown_Format;
+        }
+        if (format != kUnknown_Format) {
+            return format;
+        }
+        curr = curr->next();
+    }
+    return kUnknown_Format;
+}