cros: Enable WebUILoginView reuse.

chrome/browser/chromeos/login/ui/shared_web_view.cc

+// Copyright 2016 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/chromeos/login/ui/shared_web_view.h"
+
+#include "chrome/browser/chrome_notification_types.h"
+#include "chrome/browser/profiles/profile.h"
+#include "content/public/browser/notification_service.h"
+#include "content/public/browser/render_view_host.h"
+#include "content/public/browser/render_widget_host.h"
+#include "content/public/browser/web_contents.h"
+#include "ui/views/controls/webview/webview.h"
+
+namespace chromeos {
+
+SharedWebViewUsageHandle::SharedWebViewUsageHandle(
+    SharedWebView* shared_web_view)
+    : shared_web_view_(shared_web_view) {
+  shared_web_view_->MarkUsed();
+}
+
+SharedWebViewUsageHandle::~SharedWebViewUsageHandle() {
+  shared_web_view_->MarkUnused();
+}
+
+SharedWebView::SharedWebView(Profile* profile) : profile_(profile) {
+  registrar_.Add(this, chrome::NOTIFICATION_CLOSE_ALL_BROWSERS_REQUEST,
+                 content::NotificationService::AllSources());
+  memory_pressure_listener_ = base::MakeUnique<base::MemoryPressureListener>(
+      base::Bind(&SharedWebView::OnMemoryPressure, base::Unretained(this)));
+}
+
+SharedWebView::~SharedWebView() {
+  web_view_.reset();

[xiyuan, 2016/12/09 22:37:29]

nit: Unnecessary since Shutdown should always be called before dtor for
KeyedService.

[jdufault, 2016/12/12 18:23:09]

Done.

+}
+
+void SharedWebView::Shutdown() {
+  web_view_.reset();
+}
+
+bool SharedWebView::Get(const GURL& url, views::WebView** out_web_view) {
+  // At the moment only one shared WebView instance is supported per profile.
+  DCHECK(web_view_url_.is_empty() || web_view_url_ == url);
+  web_view_url_ = url;
+
+  // Clear cached reference if it is no longer valid (ie, destroyed in task
+  // manager).
+  if (web_view_ &&
+      !web_view_->GetWebContents()
+           ->GetRenderViewHost()
+           ->GetWidget()
+           ->GetView()) {
+    web_view_.reset();
+  }
+
+  bool reused = true;
+  if (!web_view_) {
+    web_view_ = base::MakeUnique<views::WebView>(profile_);
+    web_view_->set_owned_by_client();
+    handle_count_ = 0;
+    reused = false;
+  }
+  *out_web_view = web_view_.get();
+  return reused;
+}
+
+void SharedWebView::MarkUsed() {
+  handle_count_ += 1;

[xiyuan, 2016/12/09 22:37:29]

nit: ++handle_count_;

[jdufault, 2016/12/12 18:23:08]

Removed

+}
+
+void SharedWebView::MarkUnused() {
+  DCHECK(handle_count_ > 0);
+  handle_count_ -= 1;

[xiyuan, 2016/12/09 22:37:29]

nti: --handle_count_;

[jdufault, 2016/12/12 18:23:09]

Removed

+}
+
+void SharedWebView::Observe(int type,
+                            const content::NotificationSource& source,
+                            const content::NotificationDetails& details) {
+  DCHECK_EQ(chrome::NOTIFICATION_CLOSE_ALL_BROWSERS_REQUEST, type);
+  web_view_.reset();
+}
+
+void SharedWebView::OnMemoryPressure(
+    base::MemoryPressureListener::MemoryPressureLevel level) {
+  // Don't destroy webview on low-memory if it is actively being used.
+  if (handle_count_ > 0)
+    return;
+
+  switch (level) {
+    case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE:
+      break;
+    case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE:
+    case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL:
+      web_view_.reset();
+      break;
+  }
+}
+
+}  // namespace chromeos