WebViewProxy now propagates first responder status to the webview.

With this CL, calling becomeFirstResponder on a web view proxy makes the
potential web view first responder.

BUG=556455
R=eugenebut@chromium.org

Review URL: https://codereview.chromium.org/1646573002

Cr-Commit-Position: refs/heads/master@{#371820}

ios/web/public/web_state/crw_web_view_proxy.h

@@ -66,6 +66,9 @@
 - (UITextInputAssistantItem*)inputAssistantItem;
 #endif
 
+// Wrapper around the becomeFirstResponder method of the webview.
+- (BOOL)becomeFirstResponder;
+
 @end
 
 #endif  // IOS_WEB_PUBLIC_WEB_STATE_CRW_WEB_VIEW_PROXY_H_

ios/web/web_state/crw_web_view_proxy_impl.mm

@@ -174,4 +174,8 @@ UIView* GetFirstResponderSubview(UIView* view) {
       setKeyboardDisplayRequiresUserAction:keyboardDisplayRequiresUserAction];
 }
 
+- (BOOL)becomeFirstResponder {
+  return [_contentView becomeFirstResponder];
+}
+
 @end

ios/web/web_state/ui/crw_web_view_content_view.mm

@@ -82,6 +82,10 @@ const CGFloat kBackgroundRGBComponents[] = {0.75f, 0.74f, 0.76f};
   }
 }
 
+- (BOOL)becomeFirstResponder {
+  return [_webView becomeFirstResponder];
+}
+
 #pragma mark Accessors
 
 - (UIScrollView*)scrollView {