Add aidl file support to java builds

Add support for aidl files listed in srcs for java builds, and
an aidl_preprocess module type for framework and sdk aidls.

Change-Id: I3aa537f4483822e5b534c74d0b35f13a938f8947

common/util.go

@@ -0,0 +1,40 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// 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.
+
+package common
+
+func JoinWithPrefix(strs []string, prefix string) string {
+	if len(strs) == 0 {
+		return ""
+	}
+
+	if len(strs) == 1 {
+		return prefix + strs[0]
+	}
+
+	n := len(" ") * (len(strs) - 1)
+	for _, s := range strs {
+		n += len(prefix) + len(s)
+	}
+
+	ret := make([]byte, 0, n)
+	for i, s := range strs {
+		if i != 0 {
+			ret = append(ret, ' ')
+		}
+		ret = append(ret, prefix...)
+		ret = append(ret, s...)
+	}
+	return string(ret)
+}