Use py3 features in merge_csv.py.

- Use csv.QUOTE_MINIMAL strategy to only quote fields with special characters.
- Open file as 'r', not 'rb'.
- Use 'unix' dialect for '\n' as line terminator, instead of \r\n.

Bug: 145132366
Test: diff -w out/soong/hiddenapi/hiddenapi-greylist.csv
Change-Id: I888f3219beee5b83e53f05589a90a05f93399fe3
diff --git a/tools/hiddenapi/Android.bp b/tools/hiddenapi/Android.bp
new file mode 100644
index 0000000..e0eb06cb
--- /dev/null
+++ b/tools/hiddenapi/Android.bp
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * 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.
+ */
+
+python_binary_host {
+	name: "merge_csv",
+	main: "merge_csv.py",
+	srcs: ["merge_csv.py"],
+	version: {
+		py2: {
+			enabled: false,
+		},
+		py3: {
+			enabled: true,
+			embedded_launcher: true
+		},
+	},
+}
diff --git a/tools/hiddenapi/merge_csv.py b/tools/hiddenapi/merge_csv.py
index 48c0755..9661927 100755
--- a/tools/hiddenapi/merge_csv.py
+++ b/tools/hiddenapi/merge_csv.py
@@ -21,20 +21,19 @@
 import sys
 
 csv_readers = [
-    csv.DictReader(open(csv_file, 'rb'), delimiter=',', quotechar='|')
+    csv.DictReader(open(csv_file, 'r'), delimiter=',', quotechar='|')
     for csv_file in sys.argv[1:]
 ]
 
 # Build union of all columns from source files:
 headers = set()
 for reader in csv_readers:
-  headers = headers.union(reader.fieldnames)
+    headers = headers.union(reader.fieldnames)
 
 # Concatenate all files to output:
-out = csv.DictWriter(sys.stdout, delimiter=',', quotechar='|', fieldnames = sorted(headers))
+out = csv.DictWriter(sys.stdout, delimiter=',', quotechar='|', quoting=csv.QUOTE_MINIMAL,
+                     dialect='unix', fieldnames=sorted(headers))
 out.writeheader()
 for reader in csv_readers:
-  for row in reader:
-    out.writerow(row)
-
-
+    for row in reader:
+        out.writerow(row)