Drop build support for LEGACY_USE_JAVA7.

This flag allowed for building with an OpenJDK 7 toolchain. It was
used for build bot builds that now work with an OpenJDK 8 toolchain.
Hence, this feature is no longer required. This CL drops it.

Bug: 27583810
Test: Treehugger build succeeds.
Change-Id: I7efca363d665292bfb88f4a4d6f3a120fc8f93f3

core/droiddoc.mk

@@ -215,7 +215,7 @@ $(full_target): $(full_src_files) $(full_java_lib_deps)
                 \@$(PRIVATE_SRC_LIST_FILE) \
                 -J-Xmx1024m \
                 -XDignore.symbol.file \
-                $(if $(LEGACY_USE_JAVA7),,-Xdoclint:none) \
+                -Xdoclint:none \
                 $(PRIVATE_PROFILING_OPTIONS) \
                 $(addprefix -classpath ,$(PRIVATE_CLASSPATH)) \
                 $(addprefix -bootclasspath ,$(PRIVATE_BOOTCLASSPATH)) \

core/java_common.mk

@@ -19,12 +19,7 @@ ifeq (,$(LOCAL_JAVA_LANGUAGE_VERSION))
   ifneq (,$(filter $(LOCAL_SDK_VERSION), $(private_sdk_versions_without_any_java_18_support)))
     LOCAL_JAVA_LANGUAGE_VERSION := 1.7
   else
-    # This retains 1.7 for ART build bots only. http://b/27583810
-    ifeq (,$(LEGACY_USE_JAVA7))
-      LOCAL_JAVA_LANGUAGE_VERSION := 1.8
-    else
-      LOCAL_JAVA_LANGUAGE_VERSION := 1.7
-    endif
+    LOCAL_JAVA_LANGUAGE_VERSION := 1.8
   endif
 endif
 LOCAL_JAVACFLAGS += -source $(LOCAL_JAVA_LANGUAGE_VERSION) -target $(LOCAL_JAVA_LANGUAGE_VERSION)