Return a runtime error instead of asserting if the M4vH263Decoder fails in start()

Change-Id: Ie704a72685f749613fa0ed5fa6f461abc0406371
related-to-bug: 3328200
diff --git a/media/libstagefright/codecs/m4v_h263/dec/M4vH263Decoder.cpp b/media/libstagefright/codecs/m4v_h263/dec/M4vH263Decoder.cpp
index 0f08f6e..38778fb 100644
--- a/media/libstagefright/codecs/m4v_h263/dec/M4vH263Decoder.cpp
+++ b/media/libstagefright/codecs/m4v_h263/dec/M4vH263Decoder.cpp
@@ -132,7 +132,10 @@
     }
 
     MP4DecodingMode actualMode = PVGetDecBitstreamMode(mHandle);
-    CHECK_EQ(mode, actualMode);
+    if (mode != actualMode) {
+        PVCleanUpVideoDecoder(mHandle);
+        return UNKNOWN_ERROR;
+    }
 
     PVSetPostProcType((VideoDecControls *) mHandle, 0);