Revert 222090 "<webview>: Cleanup WebRequest event listeners whe..."

Revert 222090 "<webview>: Cleanup WebRequest event listeners whe..."

Browser test WebViewTest.Shim_TestWebRequestListenerSurvivesReparenting
failed on win xp:
http://build.chromium.org/p/chromium.win/builders/XP%20Tests%20%283%29/builds/24239

> <webview>: Cleanup WebRequest event listeners when embedder destroyed
> 
> <webivew> WebRequest event listeners should survive reparenting of the <webview> within the same embedder WebContents. Currently, event listeners are lost when the <webview> is removed from the DOM. This CL solves this problem.
> 
> Note that there is still a problem where custom elements break if the original page that created the element is closed. I have written a test that exercises this problem and I've left the test disabled until we fix the problem.
> 
> BUG=281551
> Test=WebViewTest.Shim_TestWebRequestListenerSurvivesReparenting
> 
> Review URL: https://chromiumcodereview.appspot.com/23514016

TBR=fsamuel@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=222123

[please use gerrit instead, 2013-09-09 23:14:44]

Committed patchset #1 manually as r222123.