Add reallyHasAlpha() to SkAndroidCodec

include/codec/SkAndroidCodec.h

Index: include/codec/SkAndroidCodec.h
diff --git a/include/codec/SkAndroidCodec.h b/include/codec/SkAndroidCodec.h
index f979886a43ec33c573de3553b49651a8a06d7025..9d02de06f6d5d265bddd810e9bd689b063c49edb 100644
--- a/include/codec/SkAndroidCodec.h
+++ b/include/codec/SkAndroidCodec.h
@@ -50,7 +50,7 @@ public:
     /**
      *  Format of the encoded data.
      */
-    SkEncodedFormat getEncodedFormat() const { return this->onGetEncodedFormat(); }
+    SkEncodedFormat getEncodedFormat() const { return fCodec->getEncodedFormat(); }
 
     /**
      *  Returns the dimensions of the scaled output image, for an input
@@ -208,11 +208,23 @@ public:
      */
     SkCodec::Result getAndroidPixels(const SkImageInfo& info, void* pixels, size_t rowBytes);
 
+    /**
+     *  Some images may initially report that they have alpha due to the format
+     *  of the encoded data, but then never use any colors which have alpha
+     *  less than 100%. This function can be called *after* decoding to
+     *  determine if such an image truly had alpha. Calling it before decoding
+     *  is undefined.
+     *  FIXME: see skbug.com/3582.
+     */
+    bool reallyHasAlpha() const {
+        return fCodec->reallyHasAlpha();
+    }
+
 protected:
 
-    SkAndroidCodec(const SkImageInfo&);
+    SkAndroidCodec(SkCodec*);
 
-    virtual SkEncodedFormat onGetEncodedFormat() const = 0;
+    SkCodec* codec() const { return fCodec.get(); }
 
     virtual SkISize onGetSampledDimensions(int sampleSize) const = 0;
 
@@ -226,5 +238,7 @@ private:
     // This will always be a reference to the info that is contained by the
     // embedded SkCodec.
     const SkImageInfo& fInfo;
+
+    SkAutoTDelete<SkCodec> fCodec;
 };
 #endif // SkAndroidCodec_DEFINED