Plumb bootclasspath GN -> Android Studio

build/android/gradle/android.jinja

 {# Copyright 2016 The Chromium Authors. All rights reserved. #}
 {# Use of this source code is governed by a BSD-style license that can be #}
 {# found in the LICENSE file. #}
 {% macro expand_sourceset(variables, prefix) %}
 {% if variables is defined %}
         {{ prefix }} {
             manifest.srcFile "{{ variables.android_manifest }}"
             java.srcDirs = [
 {% for path in variables.java_dirs %}
                 "{{ path }}",
 {% endfor %}
             ]
+{% if variables.java_excludes %}
             java.filter.exclude(
 {% for path in variables.java_excludes %}
                 "{{ path }}",
 {% endfor %}
             )
+{% endif %}
             jniLibs.srcDirs = [
 {% for path in variables.jni_libs %}
                 "{{ path }}",
 {% endfor %}
             ]
             res.srcDirs = [
 {% for path in variables.res_dirs %}
                 "{{ path }}",
 {% endfor %}
             ]
@@ skipping 55 matching lines @@
                 || it.name.endsWith('Resources')
                 || it.name.endsWith('ResValues')
 {% endif %}
                 || it.name.endsWith('Aidl')
                 || it.name.endsWith('Renderscript')
                 || it.name.endsWith('Shaders'))
     }
     tasksToDisable.each { Task task ->
       task.enabled = false
     }
+{% if bootclasspath is defined %}
+    tasks.withType(JavaCompile) {
+      options.bootClasspath = "{{ bootclasspath }}"
+    }
+{% endif %}
 }