[Cronet] Build cronet_impl_native_java.jar from undesugared jars

Prior to this change cronet_impl_native_java.jar was desugared but
did not include the desugar runtime library and was missing classes.
Rather than include the desugar runtime library, it's preferable to
build Java 8 jar files as that allows consumers to desugar only what
they need (e.g., not desugar try-with-resources if the consumer's
app's min-sdk-version is >= 19).
Note that this requires using either Android Studio 3.0 (currently beta)
or Bazel, which both support desugaring.

Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester
Change-Id: I68c0bc75bd11f32bf3d9e14f0a9880aa3afbf1d0
Reviewed-on: https://chromium-review.googlesource.com/620987
Reviewed-by: Helen Li <xunjieli@chromium.org>
Commit-Queue: Paul Jensen <pauljensen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#495655}

components/cronet/android/BUILD.gn

@@ -792,9 +792,9 @@ instrumentation_test_apk(
   apk_under_test = ":cronet_smoketests_platform_only_apk"
   android_manifest = "test/javatests/AndroidManifest.xml"
   deps = [
+    ":cronet_smoketests_platform_only_java",
     "//base:base_java_test_support",
     "//third_party/android_support_test_runner:runner_java",
-    ":cronet_smoketests_platform_only_java",
   ]
 
   proguard_enabled = true
@@ -935,18 +935,24 @@ action("extract_cronet_jars") {
   script = "//components/cronet/tools/extract_from_jars.py"
   depfile = "$target_gen_dir/$target_name.d"
 
-  sources = [
-    "$root_out_dir/lib.java/base/base_java.jar",
-    "$root_out_dir/lib.java/components/cronet/android/cronet_impl_native_java.jar",
-    "$root_out_dir/lib.java/net/android/net_java.jar",
-    "$root_out_dir/lib.java/url/url_java.jar",
-  ]
-
   _stamp_file = "$target_gen_dir/$target_name.stamp"
   outputs = [
     _stamp_file,
   ]
 
+  deps = [
+    ":cronet_impl_native_java",
+    "//base:base_java",
+    "//net/android:net_java",
+    "//url:url_java",
+  ]
+
+  sources = []
+  foreach(dep, deps) {
+    sources += [ get_label_info(dep, "target_gen_dir") + "/" +
+                 get_label_info(dep, "name") + "__compile_java.javac.jar" ]
+  }
+
   _rebased_sources = rebase_path(sources, root_build_dir)
 
   args = [
@@ -958,13 +964,6 @@ action("extract_cronet_jars") {
     "--stamp",
     rebase_path(_stamp_file, root_build_dir),
   ]
-
-  deps = [
-    ":cronet_impl_native_java",
-    "//base:base_java",
-    "//net/android:net_java",
-    "//url:url_java",
-  ]
 }
 
 action("repackage_extracted_jars") {