Remove support for EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9.

Prior to this change, setting that to "false" turned the default Java
language level back to 8. This change removes that option.

Also remove the unused make variable USE_OPENJDK9.

Bug: 115604102
Test: m java droid docs tests cts
Change-Id: I040cf83a2457227ffbcd1c62649e33b98c0c66f7

core/config.mk

diff --git a/core/config.mk b/core/config.mk
index 241ac8d..477d764 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -627,16 +627,6 @@
 
 EXTRACT_KERNEL := build/make/tools/extract_kernel.py
 
-USE_OPENJDK9 := true
-
-ifeq ($(EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9),)
-TARGET_OPENJDK9 := true
-else ifeq ($(EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9),true)
-TARGET_OPENJDK9 := true
-else ifeq ($(EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9),false)
-TARGET_OPENJDK9 :=
-endif
-
 # Path to tools.jar
 HOST_JDK_TOOLS_JAR := $(ANDROID_JAVA8_HOME)/lib/tools.jar
 

core/java.mk

diff --git a/core/java.mk b/core/java.mk
index d080450..99774cf1 100644
--- a/core/java.mk
+++ b/core/java.mk
@@ -358,9 +358,7 @@
 
 # Temporarily enable --multi-dex until proguard supports v53 class files
 # ( http://b/67673860 ) or we move away from proguard altogether.
-ifdef TARGET_OPENJDK9
 LOCAL_DX_FLAGS := $(filter-out --multi-dex,$(LOCAL_DX_FLAGS)) --multi-dex
-endif
 
 full_classes_pre_proguard_jar := $(LOCAL_FULL_CLASSES_JACOCO_JAR)
 

core/java_common.mk

diff --git a/core/java_common.mk b/core/java_common.mk
index dfe75f3..f6e01d2 100644
--- a/core/java_common.mk
+++ b/core/java_common.mk
@@ -33,8 +33,7 @@
     # TODO(ccross): allow 1.9 for current and unbundled once we have SDK system modules
     LOCAL_JAVA_LANGUAGE_VERSION := 1.8
   else
-    # DEFAULT_JAVA_LANGUAGE_VERSION is 1.8, unless TARGET_OPENJDK9 in which case it is 1.9
-    LOCAL_JAVA_LANGUAGE_VERSION := $(DEFAULT_JAVA_LANGUAGE_VERSION)
+    LOCAL_JAVA_LANGUAGE_VERSION := 1.9
   endif
 endif
 LOCAL_JAVACFLAGS += -source $(LOCAL_JAVA_LANGUAGE_VERSION) -target $(LOCAL_JAVA_LANGUAGE_VERSION)