Reland 1: "mac: Allow Chrome to hand off its active URL to other devices."

chrome/browser/ui/cocoa/handoff_active_url_observer.cc

Index: chrome/browser/ui/cocoa/handoff_active_url_observer.cc
diff --git a/chrome/browser/ui/cocoa/handoff_active_url_observer.cc b/chrome/browser/ui/cocoa/handoff_active_url_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..592a757408ab6233c7904badf30ee0b32485b2d2
--- /dev/null
+++ b/chrome/browser/ui/cocoa/handoff_active_url_observer.cc
@@ -0,0 +1,124 @@
+// 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 "chrome/browser/ui/cocoa/handoff_active_url_observer.h"
+
+#include "base/logging.h"
+#include "chrome/browser/ui/browser_finder.h"
+#include "chrome/browser/ui/browser_list.h"
+#include "chrome/browser/ui/cocoa/handoff_active_url_observer_delegate.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "content/public/browser/web_contents.h"
+
+HandoffActiveURLObserver::HandoffActiveURLObserver(
+    HandoffActiveURLObserverDelegate* delegate)
+    : delegate_(delegate),
+      active_tab_strip_model_(nullptr),
+      active_browser_(nullptr) {
+  DCHECK(delegate_);
+
+  active_browser_ = chrome::FindLastActiveWithHostDesktopType(
+      chrome::HOST_DESKTOP_TYPE_NATIVE);
+  BrowserList::AddObserver(this);
+  UpdateObservations();
+}
+
+HandoffActiveURLObserver::~HandoffActiveURLObserver() {
+  BrowserList::RemoveObserver(this);
+  StopObservingTabStripModel();
+  StopObservingWebContents();
+}
+
+void HandoffActiveURLObserver::OnBrowserSetLastActive(Browser* browser) {
+  active_browser_ = browser;
+  UpdateObservations();
+  delegate_->HandoffActiveURLChanged(GetActiveWebContents());
+}
+
+void HandoffActiveURLObserver::OnBrowserRemoved(Browser* removed_browser) {
+  if (active_browser_ != removed_browser)
+    return;
+
+  active_browser_ = chrome::FindLastActiveWithHostDesktopType(
+      chrome::HOST_DESKTOP_TYPE_NATIVE);
+  UpdateObservations();
+  delegate_->HandoffActiveURLChanged(GetActiveWebContents());
+}
+
+void HandoffActiveURLObserver::ActiveTabChanged(
+    content::WebContents* old_contents,
+    content::WebContents* new_contents,
+    int index,
+    int reason) {
+  StartObservingWebContents(new_contents);
+  delegate_->HandoffActiveURLChanged(new_contents);
+}
+
+void HandoffActiveURLObserver::TabStripModelDeleted() {
+  StopObservingTabStripModel();
+  StopObservingWebContents();
+}
+
+void HandoffActiveURLObserver::DidNavigateMainFrame(
+    const content::LoadCommittedDetails& details,
+    const content::FrameNavigateParams& params) {
+  delegate_->HandoffActiveURLChanged(web_contents());
+}
+
+void HandoffActiveURLObserver::WebContentsDestroyed() {
+  StopObservingWebContents();
+}
+
+void HandoffActiveURLObserver::UpdateObservations() {
+  if (!active_browser_) {
+    StopObservingTabStripModel();
+    StopObservingWebContents();
+    return;
+  }
+
+  TabStripModel* model = active_browser_->tab_strip_model();
+  StartObservingTabStripModel(model);
+
+  content::WebContents* web_contents = model->GetActiveWebContents();
+  if (web_contents)
+    StartObservingWebContents(web_contents);
+  else
+    StopObservingWebContents();
+}
+
+void HandoffActiveURLObserver::StartObservingTabStripModel(
+    TabStripModel* tab_strip_model) {
+  DCHECK(tab_strip_model);
+
+  if (active_tab_strip_model_ == tab_strip_model)
+    return;
+
+  StopObservingTabStripModel();
+  tab_strip_model->AddObserver(this);
+  active_tab_strip_model_ = tab_strip_model;
+}
+
+void HandoffActiveURLObserver::StopObservingTabStripModel() {
+  if (active_tab_strip_model_) {
+    active_tab_strip_model_->RemoveObserver(this);
+    active_tab_strip_model_ = nullptr;
+  }
+}
+
+void HandoffActiveURLObserver::StartObservingWebContents(
+    content::WebContents* web_contents) {
+  DCHECK(web_contents);
+  Observe(web_contents);
+}
+
+void HandoffActiveURLObserver::StopObservingWebContents() {
+  Observe(nullptr);
+}
+
+content::WebContents* HandoffActiveURLObserver::GetActiveWebContents() {
+  if (!active_browser_)
+    return nullptr;
+
+  return active_browser_->tab_strip_model()->GetActiveWebContents();
+}