[iOS] Upstream DomAlteringLock.

BUG=452490

Review URL: https://codereview.chromium.org/927373002

Cr-Commit-Position: refs/heads/master@{#316574}

ios/chrome/browser/web/dom_altering_lock.h

@@ -0,0 +1,64 @@
+// 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.
+
+#ifndef IOS_CHROME_BROWSER_WEB_DOM_ALTERING_LOCK_H_
+#define IOS_CHROME_BROWSER_WEB_DOM_ALTERING_LOCK_H_
+
+#include "base/ios/block_types.h"
+#import "base/ios/weak_nsobject.h"
+#include "ios/web/public/web_state/web_state_user_data.h"
+
+namespace web {
+class WebState;
+}
+
+typedef void (^ProceduralBlockWithBool)(BOOL);
+
+// This protocol must be implemented by all classes which may alter the DOM tree
+// of a web page. Before altering the DOM, the class must call
+// DOMAlteringLock::Acquire() and can only proceed if the lock is really
+// acquired.
+// After restoring the DOM tree, the class must call DOMAlteringLock::Release().
+@protocol DOMAltering<NSObject>
+
+// Method called when another class wants to acquire the lock.
+// Return YES if the class is ready to restore the DOM tree to its initial state
+// and release the lock. A call to |releaseDOMLockWithCompletionHandler:|
+// will follow to do the actual cleaning.
+// Return NO if the class wants to keep an exclusive access to the DOM tree.
+// Other features must account for the fact that they may not be able to acquire
+// a lock on the DOM and behave accordingly.
+- (BOOL)canReleaseDOMLock;
+
+// Method called when another class wants to acquire the lock.
+// The class must restore the DOM tree, call DOMAlteringLock::Release() and then
+// |completionHandler|.
+- (void)releaseDOMLockWithCompletionHandler:(ProceduralBlock)completionHandler;
+
+@end
+
+class DOMAlteringLock : public web::WebStateUserData<DOMAlteringLock> {
+ public:
+  DOMAlteringLock(web::WebState* web_state);
+
+  // This method must be called before altering the DOM of the page. This will
+  // ensure that only one class tries to alter the page at a time.
+  // The completion handler is called with YES if the lock was acquired, or NO
+  // if it could not.
+  // This method must be called on the UI thread.
+  void Acquire(id<DOMAltering> feature, ProceduralBlockWithBool lockAction);
+
+  // Releases the lock on the DOM tree.
+  // The lock is always released, even if it was acquired multiple times.
+  // This method must be called on the UI thread.
+  void Release(id<DOMAltering> feature);
+
+ private:
+  // DOMAltering object currently having the lock.
+  base::WeakNSProtocol<id<DOMAltering>> current_dom_altering_feature_;
+
+  ~DOMAlteringLock() override;
+};
+
+#endif  // IOS_CHROME_BROWSER_WEB_DOM_ALTERING_LOCK_H_

ios/chrome/browser/web/dom_altering_lock.mm

@@ -0,0 +1,48 @@
+// 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.
+
+#import "ios/chrome/browser/web/dom_altering_lock.h"
+
+#include "base/logging.h"
+#include "ios/web/public/web_thread.h"
+
+DEFINE_WEB_STATE_USER_DATA_KEY(DOMAlteringLock);
+
+DOMAlteringLock::DOMAlteringLock(web::WebState* web_state) {
+}
+
+DOMAlteringLock::~DOMAlteringLock() {
+}
+
+void DOMAlteringLock::Acquire(id<DOMAltering> feature,
+                              ProceduralBlockWithBool lockAction) {
+  DCHECK_CURRENTLY_ON_WEB_THREAD(web::WebThread::UI);
+  if (current_dom_altering_feature_.get() == feature) {
+    lockAction(YES);
+    return;
+  }
+  if (current_dom_altering_feature_) {
+    if (![current_dom_altering_feature_ canReleaseDOMLock]) {
+      lockAction(NO);
+      return;
+    }
+    [current_dom_altering_feature_ releaseDOMLockWithCompletionHandler:^() {
+      DCHECK_CURRENTLY_ON_WEB_THREAD(web::WebThread::UI);
+      DCHECK(current_dom_altering_feature_.get() == nil)
+          << "The lock must be released before calling the completion handler.";
+      current_dom_altering_feature_.reset(feature);
+      lockAction(YES);
+    }];
+    return;
+  }
+  current_dom_altering_feature_.reset(feature);
+  lockAction(YES);
+}
+
+// Release the lock on the DOM tree.
+void DOMAlteringLock::Release(id<DOMAltering> feature) {
+  DCHECK_CURRENTLY_ON_WEB_THREAD(web::WebThread::UI);
+  if (current_dom_altering_feature_.get() == feature)
+    current_dom_altering_feature_.reset();
+}

ios/chrome/ios_chrome.gyp

@@ -103,6 +103,8 @@
         'browser/ui/ui_util.mm',
         'browser/ui/uikit_ui_util.h',
         'browser/ui/uikit_ui_util.mm',
+        'browser/web/dom_altering_lock.h',
+        'browser/web/dom_altering_lock.mm',
         'browser/web_resource/ios_web_resource_service.cc',
         'browser/web_resource/ios_web_resource_service.h',
       ],