Telemetry-Autotest Integration: Run telemetry from Devservers.

As part of integrating telemetry into the autotest lab, we need the
devservers to extract and install telemetry for a given build.

BUG=chromium-os:37411
TEST=ran local devserver and through the rpc's downloaded the desired
build and made the rpc call to setup and stage telemetry and ensured
that it ran successfully.

Change-Id: I88cde49a177e484d8277369f6764e28a313dfd3e
Reviewed-on: https://gerrit.chromium.org/gerrit/43313
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Queue: Simran Basi <sbasi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
diff --git a/build_artifact.py b/build_artifact.py
index 19120e7..cf00238 100644
--- a/build_artifact.py
+++ b/build_artifact.py
@@ -280,29 +280,12 @@
     Detects whether the tarball is compressed or not based on the file
     extension and extracts the tarball into the install_path.
     """
-    # Deal with exclusions.
-    cmd = ['tar', 'xf', self.tmp_stage_path, '--directory', self.install_dir]
-
-    # Determine how to decompress.
-    tarball = os.path.basename(self.tmp_stage_path)
-    if tarball.endswith('.tar.bz2'):
-      cmd.append('--use-compress-prog=pbzip2')
-    elif tarball.endswith('.tgz') or tarball.endswith('.tar.gz'):
-      cmd.append('--gzip')
-
-    if self._exclude:
-      for exclude in self._exclude:
-        cmd.extend(['--exclude', exclude])
-
-    if self._files_to_extract:
-      cmd.extend(self._files_to_extract)
-
     try:
-      subprocess.check_call(cmd)
-    except subprocess.CalledProcessError, e:
-      raise ArtifactDownloadError(
-          'An error occurred when attempting to untar %s:\n%s' %
-          (self.tmp_stage_path, e))
+      common_util.ExtractTarball(self.tmp_stage_path, self.install_dir,
+                                 files_to_extract=self._files_to_extract,
+                                 excluded_files=self._exclude)
+    except common_util.CommonUtilError as e:
+      raise ArtifactDownloadError(str(e))
 
 
 class AutotestTarballBuildArtifact(TarballBuildArtifact):