Introduce integer constants

We can now declare a "const int" variable in an AIDL interface, in
addition to methods. These constants will become static members of the
interface/base class in the generated code.

Change-Id: I6b690ecbbe2acae37abb106510e42283f0753f26
Test: Unit and integration tests updated and pass
Bug: 23600061
Signed-off-by: Casey Dahlin <sadmac@google.com>
diff --git a/ast_java.cpp b/ast_java.cpp
index 6689111..c347d30 100644
--- a/ast_java.cpp
+++ b/ast_java.cpp
@@ -578,6 +578,13 @@
 }
 
 void
+Constant::Write(CodeWriter* to) const
+{
+    WriteModifiers(to, STATIC | FINAL | PUBLIC, ALL_MODIFIERS);
+    to->Write("int %s = %d;\n", name.c_str(), value);
+}
+
+void
 Class::Write(CodeWriter* to) const
 {
     size_t N, i;