Introduce background Download process to android

content/public/android/java/src/org/chromium/content/app/ChildProcessService.java

Index: content/public/android/java/src/org/chromium/content/app/ChildProcessService.java
diff --git a/content/public/android/java/src/org/chromium/content/app/ChildProcessService.java b/content/public/android/java/src/org/chromium/content/app/ChildProcessService.java
index 849f9c753402e4a393219a229bacde645bc97429..f2a3e2e17eab90c4fd5ff9712a4141df6417ec7f 100644
--- a/content/public/android/java/src/org/chromium/content/app/ChildProcessService.java
+++ b/content/public/android/java/src/org/chromium/content/app/ChildProcessService.java
@@ -51,6 +51,7 @@ import java.util.concurrent.atomic.AtomicReference;
 public class ChildProcessService extends Service {
     private static final String MAIN_THREAD_NAME = "ChildProcessMain";
     private static final String TAG = "ChildProcessService";
+    protected static final FileDescriptorInfo[] EMPTY_FILE_DESCRIPTOR_INFO = {};
     private IChildProcessCallback mCallback;
 
     // This is the native "Main" thread for the renderer / utility process.
@@ -289,10 +290,7 @@ public class ChildProcessService extends Service {
                 mFdInfos = new FileDescriptorInfo[fdInfosAsParcelable.length];
                 System.arraycopy(fdInfosAsParcelable, 0, mFdInfos, 0, fdInfosAsParcelable.length);
             } else {
-                // TODO(qinmin): On earlier androird versions, a started service running in another
-                // process can get killed after Chrome is killed. To work around this issue, client
-                // will never bind to the service. As a result, the file descriptors needs to be
-                // passed through an intent when starting the service.
+                mFdInfos = getFileDescriptorInfo(bundle);
             }
             Bundle sharedRelros = bundle.getBundle(Linker.EXTRA_LINKER_SHARED_RELROS);
             if (sharedRelros != null) {
@@ -412,6 +410,15 @@ public class ChildProcessService extends Service {
     }
 
     /**
+     * Retrive an array of FileDescriptorInfo from a bundle.
+     * @param bundle The bundle through the intent to launch the service.
+     * @return an array of FileDescriptorInfo.
+     */
+    protected FileDescriptorInfo[] getFileDescriptorInfo(Bundle bundle) {
+        return EMPTY_FILE_DESCRIPTOR_INFO;
+    }
+
+    /**
      * Helper for registering FileDescriptorInfo objects with GlobalFileDescriptors.
      * This includes the IPC channel, the crash dump signals and resource related
      * files.