Bump DX Java heap to 2GB.

Change-Id: I240a24f9bb8511fea8f420f76b4541018ae79a0c
diff --git a/core/definitions.mk b/core/definitions.mk
index 3a5249c..b678158 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -1525,7 +1525,7 @@
 @echo "target Dex: $(PRIVATE_MODULE)"
 @mkdir -p $(dir $@)
 $(hide) $(DX) \
-    $(if $(findstring windows,$(HOST_OS)),,-JXms16M -JXmx1536M) \
+    $(if $(findstring windows,$(HOST_OS)),,-JXms16M -JXmx2048M) \
     --dex --output=$@ \
     $(incremental_dex) \
     $(if $(NO_OPTIMIZE_DX), \