<webview>: Remove broken captureVisibleRegion code until feature is properly supported

extensions/renderer/resources/guest_view/web_view_experimental.js

Index: extensions/renderer/resources/guest_view/web_view_experimental.js
diff --git a/extensions/renderer/resources/guest_view/web_view_experimental.js b/extensions/renderer/resources/guest_view/web_view_experimental.js
index 93e117d766eb7d6289f3021b0dc5cea54fa2ec58..0e9587dbec2f71968b8c3edb7a389a1ecaf92054 100644
--- a/extensions/renderer/resources/guest_view/web_view_experimental.js
+++ b/extensions/renderer/resources/guest_view/web_view_experimental.js
@@ -19,11 +19,6 @@ WebView.prototype.maybeGetExperimentalEvents = function() {
   return {};
 };
 
-// Captures the visible content within the webview.
-WebView.prototype.captureVisibleRegion = function(spec, callback) {
-  WebViewInternal.captureVisibleRegion(this.guestInstanceId, spec, callback);
-};
-
 // Loads a data URL with a specified base URL used for relative links.
 // Optionally, a virtual URL can be provided to be shown to the user instead
 // of the data URL.
@@ -46,7 +41,6 @@ WebView.prototype.loadDataWithBaseUrl = function(
 // Registers the experimantal WebVIew API when available.
 WebView.maybeGetExperimentalAPIs = function() {
   var experimentalMethods = [
-    'captureVisibleRegion',
     'loadDataWithBaseUrl'
   ];
   return experimentalMethods;