Fix a bug where debugInfos' size wasn't being computed.

Previously debugInfos' size of 0 caused a malformed dex file
because debug data was present but not mentioned in the table
of contents.

Change-Id: I07171aaee12fef9f303fc505909f44ef1a714114
diff --git a/dx/src/com/android/dx/merge/DexMerger.java b/dx/src/com/android/dx/merge/DexMerger.java
index a6f413a..c48f436 100644
--- a/dx/src/com/android/dx/merge/DexMerger.java
+++ b/dx/src/com/android/dx/merge/DexMerger.java
@@ -33,9 +33,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.List;
-import java.util.Set;
 
 /**
  * Combine two dex files into one.
@@ -839,6 +837,7 @@
     private static final byte DBG_SET_FILE = 0x09;
 
     private void transformDebugInfoItem(DexBuffer.Section in, IndexMap indexMap) {
+        contentsOut.debugInfos.size++;
         int lineStart = in.readUleb128();
         debugInfoOut.writeUleb128(lineStart);