Updates to skimage tool to use it for testing.

src/images/SkImageDecoder_libico.cpp

Index: src/images/SkImageDecoder_libico.cpp
diff --git a/src/images/SkImageDecoder_libico.cpp b/src/images/SkImageDecoder_libico.cpp
index ffc59e0003e1ca6706f3ea985cab37d680fdc432..38883c259a38d8a6ba04e131ab60315a9907e394 100644
--- a/src/images/SkImageDecoder_libico.cpp
+++ b/src/images/SkImageDecoder_libico.cpp
@@ -20,6 +20,8 @@ public:
         return kICO_Format;
     }
 
+    virtual Format onGetFormat(SkStream*) const SK_OVERRIDE;
+
 protected:
     virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode) SK_OVERRIDE;
 
@@ -369,13 +371,7 @@ static void editPixelBit32(const int pixelNo, const unsigned char* buf,
     *address = SkPreMultiplyARGB(alpha, red, green, blue);
 }
 
-///////////////////////////////////////////////////////////////////////////////
-DEFINE_DECODER_CREATOR(ICOImageDecoder);
-/////////////////////////////////////////////////////////////////////////////////////////
-
-#include "SkTRegistry.h"
-
-static SkImageDecoder* sk_libico_dfactory(SkStream* stream) {
+static bool is_ico(SkStream* stream) {
     // Check to see if the first four bytes are 0,0,1,0
     // FIXME: Is that required and sufficient?
     SkAutoMalloc autoMal(4);
@@ -385,9 +381,29 @@ static SkImageDecoder* sk_libico_dfactory(SkStream* stream) {
     int type = read2Bytes(buf, 2);
     if (reserved != 0 || type != 1) {
         // This stream does not represent an ICO image.
-        return NULL;
+        return false;
+    }
+    return true;
+}
+
+SkImageDecoder::Format SkICOImageDecoder::onGetFormat(SkStream* stream) const {
+    if (is_ico(stream)) {
+        return kICO_Format;
+    }
+    return kUnknown_Format;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+DEFINE_DECODER_CREATOR(ICOImageDecoder);
+/////////////////////////////////////////////////////////////////////////////////////////
+
+#include "SkTRegistry.h"
+
+static SkImageDecoder* sk_libico_dfactory(SkStream* stream) {
+    if (is_ico(stream)) {
+        return SkNEW(SkICOImageDecoder);
     }
-    return SkNEW(SkICOImageDecoder);
+    return NULL;
 }
 
 static SkTRegistry<SkImageDecoder*, SkStream*> gReg(sk_libico_dfactory);