Implement basic USB device enumeration on Android.

device/usb/usb_service_android.cc

Index: device/usb/usb_service_android.cc
diff --git a/device/usb/usb_service_android.cc b/device/usb/usb_service_android.cc
index 45ce49979eccdecd82f239e7b8f3834eadc196c0..3bdf3bc6332650f8b426a8c18cff7586a36ef251 100644
--- a/device/usb/usb_service_android.cc
+++ b/device/usb/usb_service_android.cc
@@ -4,14 +4,30 @@
 
 #include "device/usb/usb_service_android.h"
 
+#include <string>
+#include <vector>
+
+#include "base/android/context_utils.h"
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/thread_task_runner_handle.h"
-#include "device/usb/usb_device.h"
+#include "device/usb/usb_device_android.h"
+#include "jni/ChromeUsbService_jni.h"
+
+using base::android::AttachCurrentThread;
+using base::android::ScopedJavaLocalRef;
 
 namespace device {
 
-UsbServiceAndroid::UsbServiceAndroid() {}
+// static
+bool UsbServiceAndroid::RegisterJNI(JNIEnv* env) {
+  return RegisterNativesImpl(env);  // Generated in ChromeUsbService_jni.h
+}
+
+UsbServiceAndroid::UsbServiceAndroid() {
+  j_object_.Reset(Java_ChromeUsbService_create(
+      AttachCurrentThread(), base::android::GetApplicationContext()));
+}
 
 UsbServiceAndroid::~UsbServiceAndroid() {}
 
@@ -20,9 +36,20 @@ scoped_refptr<UsbDevice> UsbServiceAndroid::GetDevice(const std::string& guid) {
 }
 
 void UsbServiceAndroid::GetDevices(const GetDevicesCallback& callback) {
-  std::vector<scoped_refptr<UsbDevice>> empty;
+  JNIEnv* env = AttachCurrentThread();
+  ScopedJavaLocalRef<jobjectArray> devices =
+      Java_ChromeUsbService_getDevices(env, j_object_.obj());
+  jsize length = env->GetArrayLength(devices.obj());
+
+  std::vector<scoped_refptr<UsbDevice>> results;
+  for (jsize i = 0; i < length; ++i) {
+    ScopedJavaLocalRef<jobject> raw_device(
+        env, env->GetObjectArrayElement(devices.obj(), i));
+    results.push_back(UsbDeviceAndroid::Create(env, raw_device));
+  }
+
   base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
-                                                base::Bind(callback, empty));
+                                                base::Bind(callback, results));
 }
 
 }  // namespace device