back_gesture: Do not go back at the bottom page of browser.

Bug: 1002733
Change-Id: I6254d5d5feeb1e6fa1fcb72b8109453523683b97
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1867094Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Min Chen <minch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707988}

ash/shell/shell_delegate_impl.cc

@@ -29,5 +29,9 @@ AccessibilityDelegate* ShellDelegateImpl::CreateAccessibilityDelegate() {
   return new DefaultAccessibilityDelegate;
 }
 
+bool ShellDelegateImpl::CanGoBack(gfx::NativeWindow window) const {
+  return true;
+}
+
 }  // namespace shell
 }  // namespace ash

ash/shell/shell_delegate_impl.h

@@ -23,6 +23,7 @@ class ShellDelegateImpl : public ShellDelegate {
   bool CanShowWindowForUser(const aura::Window* window) const override;
   std::unique_ptr<ScreenshotDelegate> CreateScreenshotDelegate() override;
   AccessibilityDelegate* CreateAccessibilityDelegate() override;
+  bool CanGoBack(gfx::NativeWindow window) const override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ShellDelegateImpl);

ash/shell_delegate.h

@@ -11,6 +11,7 @@
 #include "ash/ash_export.h"
 #include "base/callback.h"
 #include "base/strings/string16.h"
+#include "ui/gfx/native_widget_types.h"
 
 namespace aura {
 class Window;
@@ -37,6 +38,9 @@ class ASH_EXPORT ShellDelegate {
   // Creates a accessibility delegate. Shell takes ownership of the delegate.
   virtual AccessibilityDelegate* CreateAccessibilityDelegate() = 0;
 
+  // Check whether the current tab of the browser window can go back.
+  virtual bool CanGoBack(gfx::NativeWindow window) const = 0;
+
   virtual void OpenKeyboardShortcutHelpPage() const {}
 };
 

ash/test_shell_delegate.cc

@@ -29,4 +29,8 @@ AccessibilityDelegate* TestShellDelegate::CreateAccessibilityDelegate() {
   return new DefaultAccessibilityDelegate;
 }
 
+bool TestShellDelegate::CanGoBack(gfx::NativeWindow window) const {
+  return true;
+}
+
 }  // namespace ash

ash/test_shell_delegate.h

@@ -21,6 +21,7 @@ class TestShellDelegate : public ShellDelegate {
   bool CanShowWindowForUser(const aura::Window* window) const override;
   std::unique_ptr<ScreenshotDelegate> CreateScreenshotDelegate() override;
   AccessibilityDelegate* CreateAccessibilityDelegate() override;
+  bool CanGoBack(gfx::NativeWindow window) const override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TestShellDelegate);

ash/wm/toplevel_window_event_handler.cc

@@ -9,6 +9,7 @@
 #include "ash/public/cpp/ash_features.h"
 #include "ash/session/session_controller_impl.h"
 #include "ash/shell.h"
+#include "ash/shell_delegate.h"
 #include "ash/wm/back_gesture_affordance.h"
 #include "ash/wm/overview/overview_controller.h"
 #include "ash/wm/resize_shadow_controller.h"
@@ -104,7 +105,7 @@ void OnDragCompleted(
 }
 
 // True if we can start swiping from left edge to go to previous page.
-bool CanStartGoingBack() {
+bool CanStartGoingBack(aura::Window* target) {
   if (!features::IsSwipingFromLeftEdgeToGoBackEnabled())
     return false;
 
@@ -131,6 +132,18 @@ bool CanStartGoingBack() {
   if (shell->home_screen_controller()->IsHomeScreenVisible())
     return false;
 
+  views::Widget* widget = views::Widget::GetTopLevelWidgetForNativeView(target);
+  if (!widget)
+    return false;
+
+  aura::Window* native_window = widget->GetNativeWindow();
+  const int app_type = native_window->GetProperty(aura::client::kAppType);
+  // No need to show the back gesture affordance and go back if the active
+  // browser web contents can not go back.
+  if (app_type == static_cast<int>(AppType::BROWSER) ||
+      app_type == static_cast<int>(AppType::CHROME_APP)) {
+    return Shell::Get()->shell_delegate()->CanGoBack(widget->GetNativeWindow());
+  }
   return true;
 }
 
@@ -879,12 +892,12 @@ void ToplevelWindowEventHandler::UpdateGestureTarget(
 
 bool ToplevelWindowEventHandler::HandleGoingBackFromLeftEdge(
     ui::GestureEvent* event) {
-  if (!CanStartGoingBack())
+  aura::Window* target = static_cast<aura::Window*>(event->target());
+  if (!CanStartGoingBack(target))
     return false;
 
   gfx::Point screen_location = event->location();
-  ::wm::ConvertPointToScreen(static_cast<aura::Window*>(event->target()),
-                             &screen_location);
+  ::wm::ConvertPointToScreen(target, &screen_location);
   switch (event->type()) {
     case ui::ET_GESTURE_SCROLL_BEGIN: {
       going_back_started_ = StartedAwayFromLeftArea(event);

chrome/browser/ui/ash/chrome_shell_delegate.cc

@@ -23,6 +23,7 @@
 #include "chrome/browser/ui/browser_tabstrip.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/scoped_tabbed_browser_displayer.h"
+#include "chrome/browser/ui/views/frame/browser_view.h"
 #include "ui/aura/window.h"
 #include "url/gurl.h"
 
@@ -53,6 +54,18 @@ void ChromeShellDelegate::OpenKeyboardShortcutHelpPage() const {
   Navigate(&params);
 }
 
+bool ChromeShellDelegate::CanGoBack(gfx::NativeWindow window) const {
+  BrowserView* browser_view =
+      BrowserView::GetBrowserViewForNativeWindow(window);
+  if (!browser_view)
+    return true;
+  content::WebContents* contents =
+      browser_view->browser()->tab_strip_model()->GetActiveWebContents();
+  if (!contents)
+    return false;
+  return contents->GetController().CanGoBack();
+}
+
 ash::AccessibilityDelegate* ChromeShellDelegate::CreateAccessibilityDelegate() {
   return new ChromeAccessibilityDelegate;
 }

chrome/browser/ui/ash/chrome_shell_delegate.h

@@ -18,6 +18,7 @@ class ChromeShellDelegate : public ash::ShellDelegate {
   std::unique_ptr<ash::ScreenshotDelegate> CreateScreenshotDelegate() override;
   ash::AccessibilityDelegate* CreateAccessibilityDelegate() override;
   void OpenKeyboardShortcutHelpPage() const override;
+  bool CanGoBack(gfx::NativeWindow window) const override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ChromeShellDelegate);