Use sys._getframe(2), instead of logging.currentframe(). It's slightly faster.

PiperOrigin-RevId: 183866302
diff --git a/absl/logging/__init__.py b/absl/logging/__init__.py
index f311464..29a308d 100644
--- a/absl/logging/__init__.py
+++ b/absl/logging/__init__.py
@@ -849,7 +849,9 @@
       (filename, lineno, methodname[, sinfo]) of the calling method.
     """
     f_to_skip = ABSLLogger._frames_to_skip
-    frame = logging.currentframe()
+    # Use sys._getframe(2) instead of logging.currentframe(), it's slightly
+    # faster because there is one less frame to traverse.
+    frame = sys._getframe(2)  # pylint: disable=protected-access
 
     while frame:
       code = frame.f_code
diff --git a/absl/logging/tests/logging_test.py b/absl/logging/tests/logging_test.py
index 519d419..47903bf 100644
--- a/absl/logging/tests/logging_test.py
+++ b/absl/logging/tests/logging_test.py
@@ -375,8 +375,8 @@
     mock_frame_1.f_back = mock_frame_2
     mock_frame_0.f_back = mock_frame_1
 
-    mock.patch.object(std_logging, 'currentframe').start()
-    std_logging.currentframe.return_value = mock_frame_0
+    mock.patch.object(sys, '_getframe').start()
+    sys._getframe.return_value = mock_frame_0
 
   def setUp(self):
     self.message = 'Hello Nurse'