Upstream Chrome on iOS source code [10/11].

ios/chrome/browser/web/print_observer.mm

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ios/chrome/browser/web/print_observer.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#import "base/mac/scoped_nsobject.h"
+#include "base/values.h"
+#import "ios/chrome/browser/ui/commands/UIKit+ChromeExecuteCommand.h"
+#import "ios/chrome/browser/ui/commands/generic_chrome_command.h"
+#include "ios/chrome/browser/ui/commands/ios_command_ids.h"
+#import "ios/web/public/web_state/web_state.h"
+
+namespace {
+// Prefix for print JavaScript command.
+const char kPrintCommandPrefix[] = "print";
+}
+
+PrintObserver::PrintObserver(web::WebState* web_state)
+    : web::WebStateObserver(web_state) {
+  web_state->AddScriptCommandCallback(
+      base::Bind(&PrintObserver::OnPrintCommand, base::Unretained(this)),
+      kPrintCommandPrefix);
+}
+
+PrintObserver::~PrintObserver() {
+  Detach();
+}
+
+void PrintObserver::WebStateDestroyed() {
+  Detach();
+}
+
+bool PrintObserver::OnPrintCommand(const base::DictionaryValue&,
+                                   const GURL&,
+                                   bool) {
+  base::scoped_nsobject<GenericChromeCommand> print_command(
+      [[GenericChromeCommand alloc] initWithTag:IDC_PRINT]);
+  [web_state()->GetView() chromeExecuteCommand:print_command];
+  return true;
+}
+
+void PrintObserver::Detach() {
+  if (web_state()) {
+    web_state()->RemoveScriptCommandCallback(kPrintCommandPrefix);
+  }
+}