Shut down browser processes on Windows by sending WM_CLOSE messages.

tools/telemetry/telemetry/core/platform/win_platform_backend.py

Index: tools/telemetry/telemetry/core/platform/win_platform_backend.py
diff --git a/tools/telemetry/telemetry/core/platform/win_platform_backend.py b/tools/telemetry/telemetry/core/platform/win_platform_backend.py
index de9ec475741195492fa9b9b1674a84f39e95f404..e9d36a429904b4a2f5575108b1701ea9176c4607 100644
--- a/tools/telemetry/telemetry/core/platform/win_platform_backend.py
+++ b/tools/telemetry/telemetry/core/platform/win_platform_backend.py
@@ -6,6 +6,7 @@ import atexit
 import collections
 import contextlib
 import ctypes
+import logging
 import os
 import platform
 import re
@@ -31,6 +32,7 @@ try:
   from win32com.shell import shell  # pylint: disable=F0401
   from win32com.shell import shellcon  # pylint: disable=F0401
   import win32con  # pylint: disable=F0401
+  import win32gui  # pylint: disable=F0401
   import win32process  # pylint: disable=F0401
   import win32security  # pylint: disable=F0401
 except ImportError:
@@ -39,6 +41,7 @@ except ImportError:
   shellcon = None
   win32api = None
   win32con = None
+  win32gui = None
   win32process = None
   win32security = None
 
@@ -362,3 +365,38 @@ class WinPlatformBackend(desktop_platform_backend.DesktopPlatformBackend):
     finally:
       sock.close()
     return struct.unpack('Q', response)[0] >> start & ((1 << length) - 1)
+
+  def IsCooperativeShutdownSupported(self):
+    return True
+
+  def CooperativelyShutdown(self, proc, app_name):
+    pid = proc.pid
+
+    # http://timgolden.me.uk/python/win32_how_do_i/
+    #   find-the-window-for-my-subprocess.html
+    #
+    # It seems that intermittently this code manages to find windows
+    # that don't belong to Chrome -- for example, the cmd.exe window
+    # running slave.bat on the tryservers. Try to be careful about
+    # finding only Chrome's windows. This works for both the browser
+    # and content_shell.
+    #
+    # It seems safest to send the WM_CLOSE messages after discovering
+    # all of the sub-process's windows.
+    def find_chrome_windows(hwnd, hwnds):
+      _, win_pid = win32process.GetWindowThreadProcessId(hwnd)
+      if (pid == win_pid and
+          win32gui.IsWindowVisible(hwnd) and
+          win32gui.IsWindowEnabled(hwnd) and
+          win32gui.GetClassName(hwnd).lower().startswith(app_name)):
+        hwnds.append(hwnd)
+      return True
+    hwnds = []
+    win32gui.EnumWindows(find_chrome_windows, hwnds)
+    if hwnds:
+      for hwnd in hwnds:
+        win32gui.SendMessage(hwnd, win32con.WM_CLOSE, 0, 0)
+      return True
+    else:
+      logging.info('Did not find any windows owned by target process')
+    return False