Cronet: Fix handling of GEN_JNI packaging.

Previously, the "repackage_native" target was providing the GEN_JNI
class. When there were multiple deps containing this class, zip.py
would just choose the first one. This works right now because it grabs
//base_java's GEN_JNI and the only dep of cronet using proxy natives
is //base_java.

To allow more deps to use proxy natives, this CL adds a couple
sub-targets that are responsible for including the correct version of
GEN_JNI.

Bug: 929661, 1005836
Change-Id: Ifbcba3c012e7191be8ca410f4e8789ec791eac6a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1811974
Commit-Queue: Paul Jensen <pauljensen@chromium.org>
Reviewed-by: Paul Jensen <pauljensen@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Eric Stevenson <estevenson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699711}

components/cronet/android/BUILD.gn

@@ -732,15 +732,42 @@ repackage_jars("repackage_util") {
   ]
 }
 
+# See crbug.com/1005836 for more info on why repackage_native requires 2 extra
+# targets. These 3 targets exist to ensure the correct version of GEN_JNI
+# (a generated class containing native method definitions) is included.
 repackage_jars("repackage_native") {
   output = "$_package_dir/cronet_impl_native_java.jar"
-  deps = cronet_impl_native_java_deps_to_package + [
-           ":cronet_impl_native_base_java",
-           ":cronet_jni_registration_java",
-         ]
+  deps = [
+    ":cronet_jni_registration_java",
+    ":repackage_native_java",
+  ]
+  jar_excluded_patterns = _jar_excluded_patterns
+}
+
+_native_intermediate_jar_path = "$target_out_dir/repackage_native_impl.jar"
+
+# Do not depend on this target directly. Use :repackage_native.
+repackage_jars("repackage_native_impl") {
+  output = _native_intermediate_jar_path
+  deps = cronet_impl_native_java_deps_to_package +
+         [ ":cronet_impl_native_base_java" ]
   jar_excluded_patterns = _jar_excluded_patterns
 }
 
+# Do not depend on this target directly. Use :repackage_native.
+# This target exists to provide :repackage_native with a suitable target to
+# depend on (since dist_aar only pulls in deps of type "java_library").
+android_java_prebuilt("repackage_native_java") {
+  jar_path = _native_intermediate_jar_path
+
+  # Since only the unprocessed jar is used, no need to complete the bytecode
+  # processing steps.
+  enable_bytecode_rewriter = false
+  deps = [
+    ":repackage_native_impl",
+  ]
+}
+
 repackage_jars("repackage_common") {
   output = "$_package_dir/cronet_impl_common_java.jar"
   deps = cronet_impl_common_java_deps_to_package + [