MediaExtractor and MediaWriter fix constness

* Fixes an ugly hack, where the codec was initialized in the
InitCheck and prevented the method to be const too.

headers/os/codec/MediaExtractor.h

@@ -28,7 +28,7 @@ public:
 								//BMediaExtractor(BMediaStreamer* streamer);
 								~BMediaExtractor();
 
-			status_t			InitCheck();
+			status_t			InitCheck() const;
 
 			BDataIO*			Source() const;
 
@@ -39,7 +39,7 @@ public:
 			status_t			GetStreamMetaData(int32 stream,
 									BMetaData* data) const;
 
-			int32				CountStreams();
+			int32				CountStreams() const;
 
 			const media_format*	EncodedFormat(int32 stream);
 			int64				CountFrames(int32 stream) const;

headers/os/codec/MediaWriter.h

@@ -22,7 +22,7 @@ public:
 									const media_file_format& fileFormat);
 								~BMediaWriter();
 
-			status_t			InitCheck();
+			status_t			InitCheck() const;
 
 			BDataIO*			Target() const;
 
@@ -54,8 +54,9 @@ private:
 				void*			cookie;
 			};
 
+			status_t 			fInitCheck;
 			BDataIO*			fTarget;
-			BWriter*				fWriter;
+			BWriter*			fWriter;
 			List<StreamInfo>	fStreamInfos;
 			media_file_format	fFileFormat;
 

src/kits/codec/MediaExtractor.cpp

@@ -184,7 +184,7 @@ BMediaExtractor::~BMediaExtractor()
 
 
 status_t
-BMediaExtractor::InitCheck()
+BMediaExtractor::InitCheck() const
 {
 	CALLED();
 	return fInitStatus;
@@ -215,7 +215,7 @@ BMediaExtractor::GetMetaData(BMetaData* data) const
 
 
 int32
-BMediaExtractor::CountStreams()
+BMediaExtractor::CountStreams() const
 {
 	CALLED();
 	return fStreamCount;

src/kits/codec/MediaWriter.cpp

@@ -56,6 +56,8 @@ BMediaWriter::BMediaWriter(BDataIO* target, const media_file_format& fileFormat)
 	CALLED();
 
 	gPluginManager.CreateWriter(&fWriter, fFileFormat, fTarget);
+
+	fInitCheck = fWriter->Init(&fFileFormat);
 }
 
 
@@ -78,11 +80,11 @@ BMediaWriter::~BMediaWriter()
 
 
 status_t
-BMediaWriter::InitCheck()
+BMediaWriter::InitCheck() const
 {
 	CALLED();
 
-	return fWriter != NULL ? fWriter->Init(&fFileFormat) : B_NO_INIT;
+	return fWriter != NULL ? fInitCheck : B_NO_INIT;
 }