Fix git log command to while processing Commit position in SVNFindRev method

BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/511033002

Cr-Commit-Position: refs/heads/master@{#292285}

tools/auto_bisect/source_control.py

@@ -230,7 +230,7 @@ class GitSourceControl(SourceControl):
     # TODO(prasadv): Use an appropriate command to find commit position instead
     # of parsing the log. Resolve this once 407316 is fixed.
     commit_position_pattern = 'Cr-Commit-Position: .*@\{#(?P<commit>[0-9]+)\}'
-    cmd = ['log', '--format=%b', '-1', 'origin/master', git_revision]
+    cmd = ['log', '--format=%b', '-1', git_revision]
     output = bisect_utils.CheckRunGit(cmd, cwd=cwd)
     if output:
       version_re = re.compile(commit_position_pattern)

tools/bisect-perf-regression_test.py

@@ -265,7 +265,7 @@ class BisectPerfRegressionTest(unittest.TestCase):
         bisect_options)
 
     cp_git_rev = '7017a81991de983e12ab50dfc071c70e06979531'
-    self.assertEqual(291915, source_control.SVNFindRev(cp_git_rev))
+    self.assertEqual(291765, source_control.SVNFindRev(cp_git_rev))
 
     svn_git_rev = 'e6db23a037cad47299a94b155b95eebd1ee61a58'
     self.assertEqual(291467, source_control.SVNFindRev(svn_git_rev))