Updates to skimage tool to use it for testing.

src/images/SkImageDecoder_libbmp.cpp

Index: src/images/SkImageDecoder_libbmp.cpp
diff --git a/src/images/SkImageDecoder_libbmp.cpp b/src/images/SkImageDecoder_libbmp.cpp
index 488eddce1edb203065ce063db82e449c169db99f..68b58f5f8fd7485948ca681a9908b927ef2752c7 100644
--- a/src/images/SkImageDecoder_libbmp.cpp
+++ b/src/images/SkImageDecoder_libbmp.cpp
@@ -23,6 +23,8 @@ public:
         return kBMP_Format;
     }
 
+    virtual Format onGetFormat(SkStream*) const SK_OVERRIDE;
+
 protected:
     virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode mode) SK_OVERRIDE;
 
@@ -34,14 +36,18 @@ private:
 DEFINE_DECODER_CREATOR(BMPImageDecoder);
 ///////////////////////////////////////////////////////////////////////////////
 
-static SkImageDecoder* sk_libbmp_dfactory(SkStream* stream) {
+static bool is_bmp(SkStream* stream) {
     static const char kBmpMagic[] = { 'B', 'M' };
 
 
     char buffer[sizeof(kBmpMagic)];
 
-    if (stream->read(buffer, sizeof(kBmpMagic)) == sizeof(kBmpMagic) &&
-        !memcmp(buffer, kBmpMagic, sizeof(kBmpMagic))) {
+    return stream->read(buffer, sizeof(kBmpMagic)) == sizeof(kBmpMagic) &&
+        !memcmp(buffer, kBmpMagic, sizeof(kBmpMagic));
+}
+
+static SkImageDecoder* sk_libbmp_dfactory(SkStream* stream) {
+    if (is_bmp(stream)) {
         return SkNEW(SkBMPImageDecoder);
     }
     return NULL;
@@ -79,6 +85,13 @@ private:
     bool fJustBounds;
 };
 
+SkImageDecoder::Format SkBMPImageDecoder::onGetFormat(SkStream* stream) const {
+    if (is_bmp(stream)) {
+        return kBMP_Format;
+    }
+    return kUnknown_Format;
+}
+
 bool SkBMPImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
 
     size_t length = stream->getLength();