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 898dd6125316a907596e0a92b976f31358bcd284..0220e75613d8ffff4ec5a8f7e9b09f4bc03e39d4 100644
--- a/chrome/browser/extensions/chrome_extension_web_contents_observer.h
+++ b/chrome/browser/extensions/chrome_extension_web_contents_observer.h
@@ -59,10 +59,6 @@ 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);
 };