Revert "[ChromeDriver] Use Browser.close to quit"

This reverts commit 3edba584.

Reason for revert: Code not working properly on Mac

Original change's description:
> [ChromeDriver] Use Browser.close to quit
> 
> Currently, ChromeDriver closes desktop Chrome by simply killing the
> top-level Chrome process. This isn't graceful, and causes problems
> in some scenarios. This commit sends a Browser.close command to close
> the browser gracefully.
> 
> Bug: chromedriver:2311
> Change-Id: Idec9338b094f0aab89022b8453dd2a98268ad1e7
> Reviewed-on: https://chromium-review.googlesource.com/1037585
> Commit-Queue: John Chen <johnchen@chromium.org>
> Reviewed-by: Jonathon Kereliuk <kereliuk@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#556689}

TBR=johnchen@chromium.org,kereliuk@chromium.org

Change-Id: I53f310a7745586fdcbebb1edd58b5eb0d7873475
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromedriver:2311
Reviewed-on: https://chromium-review.googlesource.com/1049146Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556708}

chrome/test/chromedriver/chrome/chrome_desktop_impl.cc

@@ -207,15 +207,6 @@ bool ChromeDesktopImpl::IsNetworkConnectionEnabled() const {
 }
 
 Status ChromeDesktopImpl::QuitImpl() {
-  Status status = devtools_websocket_client_->ConnectIfNecessary();
-  if (status.IsOk()) {
-    status = devtools_websocket_client_->SendCommandAndIgnoreResponse(
-        "Browser.close", base::DictionaryValue());
-    if (status.IsOk() && process_.WaitForExitWithTimeout(
-                             base::TimeDelta::FromSeconds(10), nullptr))
-      return status;
-  }
-
   // If the Chrome session uses a custom user data directory, try sending a
   // SIGTERM signal before SIGKILL, so that Chrome has a chance to write
   // everything back out to the user data directory and exit cleanly. If we're