Update experimental Java 8 support to use Desugar instead of Retrolambda

build/config/android/internal_rules.gni

Index: build/config/android/internal_rules.gni
diff --git a/build/config/android/internal_rules.gni b/build/config/android/internal_rules.gni
index d7712d5363c1debd13b3113992a120d4cad1e88f..35ea57c3a0079f5cf770dfb3e3df7f85f3d437ac 100644
--- a/build/config/android/internal_rules.gni
+++ b/build/config/android/internal_rules.gni
@@ -1181,10 +1181,15 @@ if (enable_java_templates) {
         defined(invoker.supports_android) && invoker.supports_android &&
         (is_java_debug || dcheck_always_on)
 
+    #TODO(zpeng): Remove Retrolambda when Desugar is enabled.

[agrieve, 2017/07/20 00:26:52]

Can we do this now rather than checking in an if (false) statement?

[F, 2017/07/20 17:30:56]

Done.

     _retrolambda =
         defined(invoker.supports_android) && invoker.supports_android &&
         ((defined(invoker.process_java8) && invoker.process_java8) || use_java8)
 
+    _desugar = false &&
+        defined(invoker.supports_android) && invoker.supports_android &&
+        ((defined(invoker.process_java8) && invoker.process_java8) || use_java8)
+  
     _deps = []
     _previous_output_jar = _input_jar_path
 
@@ -1298,6 +1303,54 @@ if (enable_java_templates) {
       _previous_output_jar = _retrolambda_output_jar
     }
 
+    if (_desugar) {
+      _desugar_target = "${target_name}__desugar"
+      _desugar_input_jar = _previous_output_jar
+      _desugar_output_jar = "$target_out_dir/$target_name-desugar.jar"
+
+      android_sdk_jar = "$android_sdk/android.jar"
+      action(_desugar_target) {
+        script = "//build/android/gyp/desugar.py"
+        deps = _deps
+        if (defined(invoker.deps)) {
+          deps += invoker.deps
+        }
+        if (defined(invoker.public_deps)) {
+          public_deps = invoker.public_deps
+        }
+        inputs = [
+          _build_config,
+          _desugar_input_jar,
+        ]
+        outputs = [
+          _desugar_output_jar,
+        ]
+        if (defined(invoker.alternative_android_sdk_ijar)) {
+          deps += [ invoker.alternative_android_sdk_ijar_dep ]
+          _android_sdk_ijar = invoker.alternative_android_sdk_ijar
+        } else {
+          deps += [ "//build/android:android_ijar" ]
+          _android_sdk_ijar = "$root_out_dir/lib.java/android.interface.jar"
+        }
+        inputs += [ _android_sdk_ijar ]
+        args = [
+          "--input-jar",
+          rebase_path(_desugar_input_jar, root_build_dir),
+          "--output-jar",
+          rebase_path(_desugar_output_jar, root_build_dir),
+          "--classpath=@FileArg($_rebased_build_config:javac:classpath)",
+          "--android-sdk-jar",
+          rebase_path(android_sdk_jar, root_build_dir),
+          "--bootclasspath",
+          rebase_path(_android_sdk_ijar, root_build_dir),
+        ]
+      }
+
+      _deps = []
+      _deps = [ ":$_desugar_target" ]
+      _previous_output_jar = _desugar_output_jar
+    }
+    
     _output_jar_target = "${target_name}__copy"
     copy(_output_jar_target) {
       deps = _deps
@@ -2048,8 +2101,8 @@ if (enable_java_templates) {
       forward_variables_from(invoker,
                              [
                                "jar_excluded_patterns",
-                               "strip_resource_classes",
                                "process_java8",
+                               "strip_resource_classes",
                              ])
 
       visibility = [
@@ -2341,7 +2394,12 @@ if (enable_java_templates) {
     }
 
     process_java_prebuilt(_process_prebuilt_target_name) {
-      forward_variables_from(invoker, [ "jar_excluded_patterns" ])
+      forward_variables_from(invoker,
+                             [
+                               "alternative_android_sdk_ijar",
+                               "alternative_android_sdk_ijar_dep",
+                               "jar_excluded_patterns",
+                             ])
       supports_android = _supports_android
       build_config = _build_config
       input_jar_path = _javac_jar_path