desktop-pwas: Enable overscroll for app windows

Overscrolling for app windows was disabled in [1] because it was making
the Files video player slow. (old overscroll code used to take a
screenshot after each navigation and the video player was navigating
every 5 seconds). The code was later optimized to reduce the number of
screenshots taken, and eventually the code to take screenshots was
removed[2].

There is no reason why the feature has to remain disabled now that we
don't take screenshots.

[1] https://codereview.chromium.org/12082083
[2] https://chromium.googlesource.com/chromium/src/+/6e6c40b4697e889533a480fa04ffb2eb96dcda1d

Bug: 747587
Change-Id: I24b499b7f4c2f412d5efa2f687c9d96dd4cdd5f9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1659650
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669923}

chrome/browser/ui/browser.cc

@@ -1096,7 +1096,7 @@ void Browser::SetTopControlsGestureScrollInProgress(bool in_progress) {
 
 bool Browser::CanOverscrollContent() const {
 #if defined(USE_AURA)
-  return !is_app() && is_type_tabbed() &&
+  return !is_devtools() &&
          base::FeatureList::IsEnabled(features::kOverscrollHistoryNavigation);
 #else
   return false;

chrome/browser/ui/browser_browsertest.cc

@@ -1225,6 +1225,25 @@ IN_PROC_BROWSER_TEST_F(BrowserTest, AppIdSwitch) {
   EXPECT_EQ(expected_tabs, browser()->tab_strip_model()->count());
 }
 
+IN_PROC_BROWSER_TEST_F(BrowserTest, OverscrollEnabledInRegularWindows) {
+  ASSERT_TRUE(browser()->is_type_tabbed());
+  EXPECT_TRUE(browser()->CanOverscrollContent());
+}
+
+IN_PROC_BROWSER_TEST_F(BrowserTest, OverscrollEnabledInPopups) {
+  Browser* popup_browser = new Browser(
+      Browser::CreateParams(Browser::TYPE_POPUP, browser()->profile(), true));
+  ASSERT_TRUE(popup_browser->is_type_popup());
+  EXPECT_TRUE(popup_browser->CanOverscrollContent());
+}
+
+IN_PROC_BROWSER_TEST_F(BrowserTest, OverscrollDisabledInDevToolsWindows) {
+  DevToolsWindowTesting::OpenDevToolsWindowSync(browser(), false);
+  Browser* dev_tools_browser = chrome::FindLastActive();
+  ASSERT_EQ(dev_tools_browser->app_name(), DevToolsWindow::kDevToolsApp);
+  EXPECT_FALSE(dev_tools_browser->CanOverscrollContent());
+}
+
 // Open an app window and the dev tools window and ensure that the location
 // bar settings are correct.
 IN_PROC_BROWSER_TEST_F(BrowserTest, ShouldShowLocationBar) {

chrome/browser/ui/extensions/hosted_app_browsertest.cc

@@ -1459,6 +1459,12 @@ IN_PROC_BROWSER_TEST_P(HostedAppPWAOnlyTest, InstallToShelfContainsAppName) {
             base::UTF8ToUTF16("Install Manifest test app\xE2\x80\xA6"));
 }
 
+IN_PROC_BROWSER_TEST_P(HostedAppPWAOnlyTest, OverscrollEnabled) {
+  ASSERT_TRUE(https_server()->Start());
+  InstallSecurePWA();
+  EXPECT_TRUE(app_browser_->CanOverscrollContent());
+}
+
 // Tests that mixed content is not loaded inside PWA windows.
 IN_PROC_BROWSER_TEST_P(HostedAppPWAOnlyTest, MixedContentInPWA) {
   ASSERT_TRUE(https_server()->Start());