Remove command line/field trial support and configs for Isolate Extensions.

chrome/browser/extensions/chrome_extension_web_contents_observer.h

Index: chrome/browser/extensions/chrome_extension_web_contents_observer.h
diff --git a/chrome/browser/extensions/chrome_extension_web_contents_observer.h b/chrome/browser/extensions/chrome_extension_web_contents_observer.h
index 11ab88cd778902e6450d522d46974db7fa79e7d6..8711861b267775e85df2d5f338723e8abf734b0c 100644
--- a/chrome/browser/extensions/chrome_extension_web_contents_observer.h
+++ b/chrome/browser/extensions/chrome_extension_web_contents_observer.h
@@ -57,10 +57,6 @@ class ChromeExtensionWebContentsObserver
   // Reloads an extension if it is on the terminated list.
   void ReloadIfTerminated(content::RenderViewHost* render_view_host);
 
-  // Determines which bucket of a synthetic field trial this client belongs
-  // to and sets it.
-  void SetExtensionIsolationTrial(content::RenderFrameHost* render_frame_host);
-
   DISALLOW_COPY_AND_ASSIGN(ChromeExtensionWebContentsObserver);
 };