Enable Java language level 9 by default.

This changes the default Java language level from 8 to 9, i.e. javac
invocations now use -source 1.9 -target 1.9.

The environment variable EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9=false is
added to switch back to the language level 8 behaviour. (Previously,
setting that variable to true was required to opt in to language level
9.)

Test: make droid java tests cts docs
Test: javap -v <some class file in output> | grep 'major version' (reports 53, for classes from 'benchmarks' which is in Android.bp and 'ahat' which is in Android.mk)
Test: make RunBluetoothRoboTests RunCarSettingsLibRoboTests (two main flavours of robolectric)
Test: make cts && cts-tradefed help
Test: atest CtsLibcoreTestCases (reasonably low-level device tests)
Test: atest CtsHostTzDataTests (arbitrary host test)
Bug: 115604102
Change-Id: I9de888e1df021244d5e61c40934178676f09ecc7
Merged-In: I52be1817fa7121fca3bce3d8857cb9ed0825570c
diff --git a/java/sdk_test.go b/java/sdk_test.go
index 5001b47..5e0e592 100644
--- a/java/sdk_test.go
+++ b/java/sdk_test.go
@@ -279,9 +279,9 @@
 				}
 			}
 
+			// Test with legacy javac -source 1.8 -target 1.8
 			t.Run("Java language level 8", func(t *testing.T) {
-				// Test default javac -source 1.8 -target 1.8
-				config := testConfig(nil)
+				config := testConfig(map[string]string{"EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9": "false"})
 				if testcase.unbundled {
 					config.TestProductVariables.Unbundled_build = proptools.BoolPtr(true)
 				}
@@ -302,9 +302,9 @@
 				}
 			})
 
-			// Test again with javac -source 9 -target 9
+			// Test with default javac -source 9 -target 9
 			t.Run("Java language level 9", func(t *testing.T) {
-				config := testConfig(map[string]string{"EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9": "true"})
+				config := testConfig(nil)
 				if testcase.unbundled {
 					config.TestProductVariables.Unbundled_build = proptools.BoolPtr(true)
 				}
@@ -327,7 +327,8 @@
 
 			// Test again with PLATFORM_VERSION_CODENAME=REL
 			t.Run("REL", func(t *testing.T) {
-				config := testConfig(nil)
+				// TODO(b/115604102): This test should be rewritten with language level 9
+				config := testConfig(map[string]string{"EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9": "false"})
 				config.TestProductVariables.Platform_sdk_codename = proptools.StringPtr("REL")
 				config.TestProductVariables.Platform_sdk_final = proptools.BoolPtr(true)