Teach mojo_benchmark --save-traces to pull results from Android devices.

mojo/devtools/common/devtoolslib/android_shell.py

Index: mojo/devtools/common/devtoolslib/android_shell.py
diff --git a/mojo/devtools/common/devtoolslib/android_shell.py b/mojo/devtools/common/devtoolslib/android_shell.py
index a4a7d16db7261e650c0c776564dc35a6655e537b..abda378e68225c2a29d8da0efe049d013cc3b84c 100644
--- a/mojo/devtools/common/devtoolslib/android_shell.py
+++ b/mojo/devtools/common/devtoolslib/android_shell.py
@@ -199,6 +199,21 @@ class AndroidShell(Shell):
     return len(subprocess.check_output(self._adb_command([
         'shell', 'pm', 'list', 'packages', _MOJO_SHELL_PACKAGE_NAME]))) > 0
 
+  @staticmethod
+  def get_tmp_dir_path():
+    """Returns a path to a cache directory owned by the shell where temporary
+    files can be stored.
+    """
+    return '/data/data/%s/cache/tmp/' % _MOJO_SHELL_PACKAGE_NAME
+
+  def pull_file(self, device_path, destination_path, remove_original=False):
+    """Copies or moves the specified file on the device to the host."""
+    subprocess.check_call(self._adb_command([
+        'pull', device_path, destination_path]))
+    if remove_original:
+      subprocess.check_call(self._adb_command([
+          'shell', 'rm', device_path]))
+
   def check_device(self, require_root=False):
     """Verifies if the device configuration allows adb to run.