Make build_command_buffer.py work on Windows

BUG=skia:4957
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1710983002

Review URL: https://codereview.chromium.org/1710983002
diff --git a/tools/build_command_buffer.py b/tools/build_command_buffer.py
index 4c8460b..e57f496 100755
--- a/tools/build_command_buffer.py
+++ b/tools/build_command_buffer.py
@@ -87,6 +87,26 @@
 
   chrome_target_dir_rel = os.path.join('out', args.chrome_build_type)
 
+  # The command buffer shared library will have a different name on Linux,
+  # Mac, and Windows. Also, on Linux it will be in a 'lib' subdirectory and
+  # needs to be placed in a 'lib' subdirectory of the directory containing the
+  # Skia executable. Also, the name of the gclient executable we call out to has
+  # a .bat file extension on Windows.
+  platform = sys.platform
+  if platform == 'cygwin':
+    platform = 'win32'
+
+  shared_lib_name = 'libcommand_buffer_gles2.so'
+  shared_lib_subdir = 'lib'
+  gclient = 'gclient'
+  if platform == 'darwin':
+    shared_lib_name = 'libcommand_buffer_gles2.dylib'
+    shared_lib_subdir = ''
+  elif platform == 'win32':
+    shared_lib_name = 'command_buffer_gles2.dll'
+    shared_lib_subdir = ''
+    gclient = 'gclient.bat'
+
   if not args.no_sync:
     try:
       subprocess.check_call(['git', 'fetch'], cwd=chrome_src_dir)
@@ -104,7 +124,7 @@
   if not args.no_sync:
     try:
       os.environ['GYP_GENERATORS'] = 'ninja'
-      subprocess.check_call(['gclient', 'sync', '--reset', '--force'],
+      subprocess.check_call([gclient, 'sync', '--reset', '--force'],
           cwd=chrome_src_dir)
     except subprocess.CalledProcessError as error:
       sys.exit('Error (ret code: %s) calling "%s" in %s' % error.returncode,
@@ -118,23 +138,6 @@
     sys.exit('Error (ret code: %s) calling "%s" in %s' % error.returncode,
         error.cmd, chrome_src_dir)
 
-  # The command buffer shared library will have a different extension on Linux,
-  # Mac, and Windows. Also, on Linux it will be in a 'lib' subdirectory and
-  # needs to be placed in a 'lib' subdirectory of the directory containing the
-  # Skia executable.
-  platform = sys.platform
-  if platform == 'cygwin':
-    platform = 'win32'
-
-  shared_lib_ext = '.so'
-  shared_lib_subdir = 'lib'
-  if platform == 'darwin':
-    shared_lib_ext = '.dylib'
-    shared_lib_subdir = ''
-  elif platform == 'win32':
-    shared_lib_ext = '.dll'
-    shared_lib_subdir = ''
-
   shared_lib_src_dir = os.path.join(chrome_src_dir, chrome_target_dir_rel,
                                     shared_lib_subdir)
   shared_lib_dst_dir = os.path.join(args.output_dir, shared_lib_subdir)
@@ -142,7 +145,6 @@
   if shared_lib_subdir and not os.path.isdir(shared_lib_dst_dir):
     os.mkdir(shared_lib_dst_dir)
 
-  shared_lib_name = 'libcommand_buffer_gles2' + shared_lib_ext
   shared_lib_src = os.path.join(shared_lib_src_dir, shared_lib_name)
   shared_lib_dst = os.path.join(shared_lib_dst_dir, shared_lib_name)