Bug 1159456 - Finish and exit from Flush() even if MFTManager rejects sample. r=cpearce, a=sledru

dom/media/fmp4/wmf/WMFMediaDataDecoder.cpp

@@ -134,7 +134,7 @@ WMFMediaDataDecoder::Decode()
         PurgeInputQueue();
       }
       mCallback->Error();
-      return;
+      continue; // complete flush if flushing
     }
 
     mLastStreamOffset = input->byte_offset;