Only run git once in gdbinit

Running git is fairly slow. Removing this call improves gdb attach
time from 34 sec to 27 sec (20.5%). It is also completely
unnecessary, because we only need to load pretty printers once.

R=thomasanderson@chromium.org

Change-Id: I47de8cf198040d46dfdcaa22cc6c3f7d661d28ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1863069
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Auto-Submit: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705967}

tools/gdb/gdbinit

@@ -9,7 +9,7 @@ import subprocess
 import sys
 
 compile_dirs = set()
-
+src_dir = None
 
 def get_current_debug_file_directories():
   dir = gdb.execute("show debug-file-directory", to_string=True)
@@ -47,6 +47,25 @@ def load_gdb_chrome(src_dir):
   gdb.execute('source %s' % os.path.join(tools_gdb, 'viewg.gdb'))
 
 
+def set_src_dir(compile_dir):
+  global src_dir
+  git = subprocess.Popen(
+      ['git', '-C', compile_dir, 'rev-parse', '--show-toplevel'],
+      stdout=subprocess.PIPE,
+      stderr=subprocess.PIPE)
+  src_dir, _ = git.communicate()
+  if git.returncode:
+    return
+  if isinstance(src_dir, str):
+    src_dir = src_dir.rstrip()
+  else:
+    src_dir = src_dir.decode('utf-8').rstrip()
+
+  load_libcxx_pretty_printers(src_dir)
+
+  load_gdb_chrome(src_dir)
+
+
 def newobj_handler(event):
   global compile_dirs
   compile_dir = os.path.dirname(event.new_objfile.filename)
@@ -64,21 +83,9 @@ def newobj_handler(event):
   # https://crbug.com/603286#c35
   add_debug_file_directory(compile_dir)
 
-  git = subprocess.Popen(
-      ['git', '-C', compile_dir, 'rev-parse', '--show-toplevel'],
-      stdout=subprocess.PIPE,
-      stderr=subprocess.PIPE)
-  src_dir, _ = git.communicate()
-  if git.returncode:
-    return
-  if isinstance(src_dir, str):
-    src_dir = src_dir.rstrip()
-  else:
-    src_dir = src_dir.decode('utf-8').rstrip()
-
-  load_libcxx_pretty_printers(src_dir)
-
-  load_gdb_chrome(src_dir)
+  global src_dir
+  if not src_dir:
+    set_src_dir(compile_dir)
 
 
 # Event hook for newly loaded objfiles.