skpbench: simplify adb and reduce number of invocations

tools/skpbench/_adb.py

 # Copyright 2016 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+from __future__ import print_function
 import re
 import subprocess
 import sys
 
 class Adb:
-  def __init__(self, device_serial=None):
+  def __init__(self, device_serial=None, echofile=None):
     self.__invocation = ['adb']
     if device_serial:
       self.__invocation.extend(['-s', device_serial])
+    self.__echofile = echofile
+    self.__is_root = None
 
   def shell(self, cmd):
+    if self.__echofile:
+      self.__echo_cmd(cmd)
     subprocess.call(self.__invocation + ['shell', cmd], stdout=sys.stderr)
 
   def check(self, cmd):
+    if self.__echofile:
+      self.__echo_cmd(cmd)
     result = subprocess.check_output(self.__invocation + ['shell', cmd])
-    return result.rstrip()
+    if self.__echofile:
+      print(result, file=self.__echofile)
+    return result
 
-  def check_lines(self, cmd):
-    result = self.check(cmd)
-    return re.split('[\r\n]+', result)
-
-  def get_device_model(self):
-    result = self.check('getprop | grep ro.product.model')
-    result = re.match(r'\[ro.product.model\]:\s*\[(.*)\]', result)
-    return result.group(1) if result else 'unknown_product'
+  def root(self):
+    if not self.is_root():
+      subprocess.call(self.__invocation + ['root'], stdout=sys.stderr)
+      self.__is_root = None
+    return self.is_root()
 
   def is_root(self):
-    return self.check('whoami') == 'root'
-
-  def attempt_root(self):
-    if self.is_root():
-      return True
-    subprocess.call(self.__invocation + ['root'], stdout=sys.stderr)
-    return self.is_root()
+    if self.__is_root is None:
+      self.__is_root = ('root' == self.check('whoami').strip())
+    return self.__is_root
 
   def remount(self):
     subprocess.call(self.__invocation + ['remount'], stdout=sys.stderr)
+
+  def __echo_cmd(self, cmd):
+    escaped = [re.sub(r'([^a-zA-Z0-9])', r'\\\1', x)
+               for x in cmd.strip().splitlines()]
+    subprocess.call(self.__invocation + \
+                    ['shell', 'echo', '$(whoami)@$(getprop ro.serialno)$',
+                     " '\n>' ".join(escaped)],
+                    stdout=self.__echofile)