Hide Value class constructor

Value class was constructable and it had hidden abstract methods.
This is an issue, Changing to private constructor so that internal
implementors can still call it, but this class can no longer be
implemented by external implementors.

Test: make update-api
Change-Id: Ifb9849e478cff31d0ad2d2fd5d518c207a8764eb
diff --git a/tools/ahat/etc/ahat_api.txt b/tools/ahat/etc/ahat_api.txt
index 89f01b6..9898af4 100644
--- a/tools/ahat/etc/ahat_api.txt
+++ b/tools/ahat/etc/ahat_api.txt
@@ -294,7 +294,6 @@
   }
 
   public abstract class Value {
-    ctor public Value();
     method public com.android.ahat.heapdump.AhatInstance asAhatInstance();
     method public Byte asByte();
     method public Character asChar();
diff --git a/tools/ahat/src/main/com/android/ahat/heapdump/Value.java b/tools/ahat/src/main/com/android/ahat/heapdump/Value.java
index 5e48dca..1f9bb96 100644
--- a/tools/ahat/src/main/com/android/ahat/heapdump/Value.java
+++ b/tools/ahat/src/main/com/android/ahat/heapdump/Value.java
@@ -24,6 +24,7 @@
  * instance from the heap dump.
  */
 public abstract class Value {
+  Value() { }
   /**
    * Constructs a Value for an AhatInstance.
    * Note: returns null for null <code>value</code>.