generate_gradle.py: Allow multiple --target and add --all

build/android/gradle/build.gradle.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. #}
 // Generated by //build/android/generate_gradle.py
 {% if template_type == 'root' %}
 
 buildscript {
     repositories {
         jcenter()
     }
     dependencies {
         classpath "com.android.tools.build:gradle:2.2.0"
     }
 }
 
 {% elif template_type == 'java_library' %}
 
 apply plugin: "java"
 
 sourceSets {
     main {
-        java.srcDirs = {{ java_dirs }}
+        java.srcDirs = [
+{% for path in java_dirs %}
+            "{{ path }}",
+{% endfor %}
+        ]
     }
 }
 
 sourceCompatibility = JavaVersion.VERSION_1_7
 targetCompatibility = JavaVersion.VERSION_1_7
 
 {% else %}
 
 {% if template_type == 'android_library' %}
 apply plugin: "com.android.library"
@@ skipping 56 matching lines @@
                 || it.name.endsWith('Aidl')
                 || it.name.endsWith('Renderscript')
                 || it.name.endsWith('Shaders'))
     }
     tasksToDisable.each { Task task ->
       task.enabled = false
     }
 }
 
 {% endif %}