Fix of uninitialized mIsDrm variable.

The mIsDrm is a bool that isn't initialized.
This causes it to be true in most default cases.

Change-Id: I41b534514bf6a3ca88a9f0994b814d55fcd7453b
diff --git a/include/media/stagefright/MediaExtractor.h b/include/media/stagefright/MediaExtractor.h
index 94090ee..3076a96 100644
--- a/include/media/stagefright/MediaExtractor.h
+++ b/include/media/stagefright/MediaExtractor.h
@@ -67,7 +67,7 @@
     }
 
 protected:
-    MediaExtractor() {}
+    MediaExtractor() : mIsDrm(false) {}
     virtual ~MediaExtractor() {}
 
 private: