[Telemetry] Don't wait for browsers to stop after killing them.

tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py

Index: tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py b/tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py
index b1ab679e07db1747b1b576a09b5127630ab1fcff..7130a312be08db029975e17620ebf305d4acbb9f 100644
--- a/tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py
+++ b/tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py
@@ -329,13 +329,7 @@ class DesktopBrowserBackend(chrome_browser_backend.ChromeBrowserBackend):
     # Shutdown aggressively if the above failed or if the profile is temporary.
     if self.IsBrowserRunning():
       self._proc.kill()
-
-    try:
-      util.WaitFor(lambda: not self.IsBrowserRunning(), timeout=10)
-    except util.TimeoutException:
-      raise Exception('Could not shutdown the browser.')
-    finally:
-      self._proc = None
+    self._proc = None
 
     if self._crash_service:
       self._crash_service.kill()