SuperSize: Make it faster to exit console

Use os._exit() to skip atexit() and __exit__() functions.
Saves 2-5 seconds of nothingness after you hit Ctrl-D to exit.

Bug: None
Change-Id: I69cc80fc8e56e42b7670db80222556738948f6af
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2956312
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#892562}

tools/binary_size/libsupersize/console.py

@@ -5,7 +5,6 @@
 """An interactive console for looking analyzing .size files."""
 
 import argparse
-import atexit
 import code
 import contextlib
 import itertools
@@ -32,7 +31,6 @@
 # Number of lines before using less for Print().
 _THRESHOLD_FOR_PAGER = 50
 
-
 @contextlib.contextmanager
 def _LessPipe():
   """Output to `less`. Yields a file object to write to."""
@@ -70,8 +68,19 @@ def _WriteToStream(lines, use_pager=None, to_file=None):
     describe.WriteLines(lines, sys.stdout.write)
 
 
+@contextlib.contextmanager
+def _ReadlineSession():
+  history_file = os.path.join(os.path.expanduser('~'),
+                              '.binary_size_query_history')
+  # Without initializing readline, arrow keys don't even work!
+  readline.parse_and_bind('tab: complete')
+  if os.path.exists(history_file):
+    readline.read_history_file(history_file)
+  yield
+  readline.write_history_file(history_file)
+
+
 class _Session(object):
-  _readline_initialized = False
 
   def __init__(self, size_infos, output_directory_finder, tool_prefix_finder):
     self._printed_variables = []
@@ -485,26 +494,12 @@ def keys(cls, super_keys=None):
     lines.append('*' * 80)
     return '\n'.join(lines)
 
-
-  @classmethod
-  def _InitReadline(cls):
-    if cls._readline_initialized:
-      return
-    cls._readline_initialized = True
-    # Without initializing readline, arrow keys don't even work!
-    readline.parse_and_bind('tab: complete')
-    history_file = os.path.join(os.path.expanduser('~'),
-                                '.binary_size_query_history')
-    if os.path.exists(history_file):
-      readline.read_history_file(history_file)
-    atexit.register(lambda: readline.write_history_file(history_file))
-
   def Eval(self, query):
     exec (query, self._variables)
 
   def GoInteractive(self):
-    _Session._InitReadline()
-    code.InteractiveConsole(self._variables).interact(self._CreateBanner())
+    with _ReadlineSession():
+      code.InteractiveConsole(self._variables).interact(self._CreateBanner())
 
 
 def AddArguments(parser):
@@ -552,3 +547,10 @@ def Run(args, on_config_error):
   else:
     logging.info('Entering interactive console.')
     session.GoInteractive()
+
+  # Exit without running GC, which can save multiple seconds due the large
+  # number of objects created. It meants atexit and __del__ calls are not
+  # made, but this shouldn't matter for console.
+  sys.stdout.flush()
+  sys.stderr.flush()
+  os._exit(0)