Avoid unnecessary object allocation in CryptoInfo.set

This is causing a large number of unnecessary small object allocations
during encrypted playbacks, which presumably all need to be GC'd.

I wasn't sure whether the zero pattern should be static; that might
be objectionable in the platform (unsure?), since it would live
forever from the point of the class being classloaded. It doesn't
make much/any difference in practice in any case.

Test: Safe refactoring CL.
Change-Id: I9ee5fe284b0f854d672d83b97fc51116b0416f91

media/java/android/media/MediaCodec.java

@@ -2441,6 +2441,8 @@ final public class MediaCodec {
             }
         };
 
+        private final Pattern zeroPattern = new Pattern(0, 0);
+
         /**
          * The pattern applicable to the protected data in each subsample.
          */
@@ -2463,7 +2465,7 @@ final public class MediaCodec {
             key = newKey;
             iv = newIV;
             mode = newMode;
-            pattern = new Pattern(0, 0);
+            pattern = zeroPattern;
         }
 
         /**