Add waitForService to AIDL.

Eye towards:
- avoiding while(true) getService loops
- need it to make AIDL dynamic HALs
- need it for feature parity w/ HIDL

Bug: 136027762
Test: use in AIDL unit test
Change-Id: I2981eb4ebecff8c4519e09b7dcca51892dfd528d
diff --git a/cmds/dumpsys/tests/dumpsys_test.cpp b/cmds/dumpsys/tests/dumpsys_test.cpp
index 3ada153..cbac839 100644
--- a/cmds/dumpsys/tests/dumpsys_test.cpp
+++ b/cmds/dumpsys/tests/dumpsys_test.cpp
@@ -53,7 +53,7 @@
     MOCK_CONST_METHOD1(checkService, sp<IBinder>(const String16&));
     MOCK_METHOD4(addService, status_t(const String16&, const sp<IBinder>&, bool, int));
     MOCK_METHOD1(listServices, Vector<String16>(int));
-
+    MOCK_METHOD1(waitForService, sp<IBinder>(const String16&));
   protected:
     MOCK_METHOD0(onAsBinder, IBinder*());
 };