Qualify the return value of SkImageDecoder::decode

src/images/SkScaledBitmapSampler.cpp

Index: src/images/SkScaledBitmapSampler.cpp
diff --git a/src/images/SkScaledBitmapSampler.cpp b/src/images/SkScaledBitmapSampler.cpp
index d78502d2bbd6a3727de5081fcdf3652cfcd6ba45..fe425d58b1cab09ac744114a18b8d0184049391a 100644
--- a/src/images/SkScaledBitmapSampler.cpp
+++ b/src/images/SkScaledBitmapSampler.cpp
@@ -835,8 +835,8 @@ class DummyDecoder : public SkImageDecoder {
 public:
     DummyDecoder() {}
 protected:
-    virtual bool onDecode(SkStream*, SkBitmap*, SkImageDecoder::Mode) SK_OVERRIDE {
-        return false;
+    virtual Result onDecode(SkStream*, SkBitmap*, SkImageDecoder::Mode) SK_OVERRIDE {
+        return kFailure;
     }
 };