[Cronet] Build maven modules and test by building sample app with gradle

This change builds maven modules for Cronet.
Each maven module includes:
  1. POM file defining module and listing dependent modules
  2. Jars
  3. Proguard files (optional)
  4. Native libraries (optional)
  5. Resources (optional)
  6. Javadocs (optional)
We build four maven modules:
  1. cronet-api: the Cronet API
  2. cronet-embedded: the Cronet native implementation
  3. cronet-fallback: the Cronet fallback implementation
  4. cronet-common: Cronet implementation in common with #3 and #4

To test the maven modules, this change builds the Cronet sample app using gradle.
You can install and run the resulting app by:
  ninja -C out/Debug cronet_maven_test_build
  adb install -r out/Debug/cronet_maven/test/build/outputs/apk/debug/test-debug.apk
  adb install -r out/Debug/cronet_maven/test/build/outputs/apk/androidTest/debug/test-debug-androidTest.apk
  adb shell am instrument -w org.chromium.cronet_sample_apk.test/android.support.test.runner.AndroidJUnitRunner

Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I5ed27e86f3e01dc3a6441ab449bbe942553343af
Reviewed-on: https://chromium-review.googlesource.com/998019
Commit-Queue: Paul Jensen <[email protected]>
Reviewed-by: Andrei Kapishnikov <[email protected]>
Reviewed-by: Eric Stevenson <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#554608}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 10f4dd8996fe4a028ee2aa61cdf84ad4080ef31c

config/android/rules.gni

@@ -1510,6 +1510,7 @@ if (enable_java_templates) {
   #   proguard_configs: List of proguard configs (optional).
   #   android_manifest: Path to AndroidManifest.xml (optional).
   #   native_libraries: list of native libraries (optional).
+  #   direct_deps_only: Do not recurse on deps. (optional, defaults false).
   #
   # Example
   #   dist_aar("my_aar") {
@@ -1524,6 +1525,9 @@ if (enable_java_templates) {
       _deps = invoker.deps
     }
 
+    _direct_deps_only =
+        defined(invoker.direct_deps_only) && invoker.direct_deps_only
+
     _build_config = "$target_gen_dir/$target_name.build_config"
     _build_config_target_name = "${target_name}__build_config"
 
@@ -1566,11 +1570,15 @@ if (enable_java_templates) {
         rebase_path(depfile, root_build_dir),
         "--output",
         rebase_path(invoker.output, root_build_dir),
-        "--jars=@FileArg($_rebased_build_config:deps_info:javac_full_classpath)",
         "--dependencies-res-zips=@FileArg($_rebased_build_config:resources:dependency_zips)",
         "--r-text-files=@FileArg($_rebased_build_config:resources:extra_r_text_files)",
         "--proguard-configs=@FileArg($_rebased_build_config:deps_info:proguard_all_configs)",
       ]
+      if (_direct_deps_only) {
+        args += [ "--jars=@FileArg($_rebased_build_config:javac:classpath)" ]
+      } else {
+        args += [ "--jars=@FileArg($_rebased_build_config:deps_info:javac_full_classpath)" ]
+      }
       if (defined(invoker.android_manifest)) {
         args += [
           "--android-manifest",