Android: Use d8 to desugar for is_java_debug

Still need to work through some size regressions before enabling in
release.

Bug: 1032609
Change-Id: I842052f81642f1e99371102a3d3b9c9876a20148
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2133880
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Sam Maier <smaier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756139}

build/config/android/config.gni

@@ -68,6 +68,9 @@ if (is_android || is_chromeos) {
     }
   }
 
+  # Our build rules support only KitKat+.
+  default_min_sdk_version = 19
+
   if (!defined(default_android_ndk_root)) {
     default_android_ndk_root = "//third_party/android_ndk"
     default_android_ndk_version = "r20"
@@ -232,7 +235,7 @@ if (is_android || is_chromeos) {
     java_warnings_as_errors = !is_java_debug
 
     # Desugar with D8 rather than Desugar tool.
-    desugar_with_d8 = false
+    desugar_with_d8 = is_java_debug
   }
 
   # Path to where selected build variables are written to.

build/config/android/internal_rules.gni

@@ -858,7 +858,7 @@ if (enable_java_templates) {
         lint_suppressions_file = "//build/android/lint/suppressions.xml"
       }
 
-      _min_sdk_version = 19
+      _min_sdk_version = default_min_sdk_version
       if (defined(invoker.min_sdk_version)) {
         _min_sdk_version = invoker.min_sdk_version
       }
@@ -1146,22 +1146,31 @@ if (enable_java_templates) {
   #   disable_incremental: Disable incremental dexing.
   template("dex") {
     assert(defined(invoker.output))
+    _min_sdk_version = default_min_sdk_version
+    if (defined(invoker.min_sdk_version)) {
+      _min_sdk_version = invoker.min_sdk_version
+    }
 
     _proguard_enabled =
         defined(invoker.proguard_enabled) && invoker.proguard_enabled
     _proguarding_with_r8 =
         _proguard_enabled && !defined(invoker.proguard_jar_path)
     _enable_multidex =
         !defined(invoker.enable_multidex) || invoker.enable_multidex
-    _enable_main_dex_list =
-        _enable_multidex &&
-        (!defined(invoker.min_sdk_version) || invoker.min_sdk_version < 21)
+    _enable_main_dex_list = _enable_multidex && _min_sdk_version < 21
     if (!_enable_main_dex_list) {
       if (defined(invoker.negative_main_dex_globs)) {
         not_needed(invoker, [ "negative_main_dex_globs" ])
       }
     }
 
+    # When using d8 to desugar, the dex merge step must not be set to a higher
+    # minSdkVersion than the libraries in order for the proper backported
+    # methods to be included.
+    if (invoker.enable_desugar && defined(invoker.input_dex_filearg)) {
+      _min_sdk_version = default_min_sdk_version
+    }
+
     assert(!_proguard_enabled || !(defined(invoker.input_dex_filearg) ||
                                        defined(invoker.input_classes_filearg) ||
                                        defined(invoker.input_class_jars)),
@@ -1214,6 +1223,7 @@ if (enable_java_templates) {
         args = [
           "--proguard-configs=@FileArg($_rebased_build_config:deps_info:proguard_all_configs)",
           "--input-paths=@FileArg($_rebased_build_config:deps_info:java_runtime_classpath)",
+          "--min-api=$_min_sdk_version",
         ]
         if (defined(invoker.proguard_args)) {
           args += invoker.proguard_args
@@ -1232,13 +1242,6 @@ if (enable_java_templates) {
           args += [ "--apply-mapping=$_rebased_apply_mapping_path" ]
         }
 
-        if (defined(invoker.min_sdk_version)) {
-          args += [
-            "--min-api",
-            "${invoker.min_sdk_version}",
-          ]
-        }
-
         if (_proguarding_with_r8 && _enable_main_dex_list) {
           if (defined(invoker.extra_main_dex_proguard_config)) {
             args += [
@@ -1368,6 +1371,7 @@ if (enable_java_templates) {
           rebase_path(depfile, root_build_dir),
           "--output",
           rebase_path(outputs[0], root_build_dir),
+          "--min-api=$_min_sdk_version",
         ]
 
         if (_proguard_enabled) {
@@ -1441,13 +1445,6 @@ if (enable_java_templates) {
           args += [ "--release" ]
         }
 
-        if (defined(invoker.min_sdk_version)) {
-          args += [
-            "--min-api",
-            "${invoker.min_sdk_version}",
-          ]
-        }
-
         if (invoker.enable_desugar) {
           args += [
             "--desugar",

build/config/android/rules.gni

@@ -1363,7 +1363,7 @@ if (enable_java_templates) {
         android_manifest = "//build/android/AndroidManifest.xml"
       }
       arsc_output = _resource_arsc_output
-      min_sdk_version = 19
+      min_sdk_version = default_min_sdk_version
       target_sdk_version = 23
     }
 
@@ -1852,7 +1852,7 @@ if (enable_java_templates) {
       supports_android = true
       requires_android = true
       if (!defined(invoker.min_sdk_version)) {
-        min_sdk_version = 19
+        min_sdk_version = default_min_sdk_version
       }
 
       if (!defined(jar_excluded_patterns)) {
@@ -2104,7 +2104,7 @@ if (enable_java_templates) {
   #     static_library_provider target will provide the dex file(s) for this
   #     target.
   #   min_sdk_version: The minimum Android SDK version this target supports.
-  #     Optional, default 19.
+  #     Optional, default $default_min_sdk_version.
   #   target_sdk_version: The target Android SDK version for this target.
   #     Optional, default 23.
   #   max_sdk_version: The maximum Android SDK version this target supports.
@@ -2137,7 +2137,7 @@ if (enable_java_templates) {
     _build_config = "$target_gen_dir/$target_name.build_config"
     _build_config_target = "$target_name$build_config_target_suffix"
 
-    _min_sdk_version = 19
+    _min_sdk_version = default_min_sdk_version
     _target_sdk_version = 23
     if (defined(invoker.min_sdk_version)) {
       _min_sdk_version = invoker.min_sdk_version