Homescreen: Port homescreen workload to WA3

Just did:  wlauto      -> wa
           self.device -> self.target

wa/workloads/homescreen/__init__.py

@@ -0,0 +1,41 @@
+#    Copyright 2013-2017 ARM Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# pylint: disable=E1101
+
+from wa import Workload, Parameter
+
+
+class HomeScreen(Workload):
+
+    name = 'homescreen'
+    description = """
+    A workload that goes to the home screen and idles for the the
+    specified duration.
+
+    """
+    supported_platforms = ['android']
+
+    parameters = [
+        Parameter('duration', kind=int, default=20,
+                  description='Specifies the duration, in seconds, of this workload.'),
+    ]
+
+    def setup(self, context):
+        self.target.clear_logcat()
+        self.target.execute('input keyevent 3')  # press the home key
+
+    def run(self, context):
+        self.target.sleep(self.duration)