Disable overscroll on Windows machines w/o touchscreen.

Currently GestureNav/horizontal overscroll is enabled on all Aura builds. However to engage GestureNav you either need a touch screen or a 2-finger gesture support for the touchpad. This means we are paying the cost of screenshotting for every navigation on some machines where you won't ever be able to experience GestureNav.

BUG=398516

Review URL: https://codereview.chromium.org/617543002

Cr-Commit-Position: refs/heads/master@{#297771}

chrome/browser/ui/browser.cc

@@ -201,6 +201,7 @@
 #include "chrome/browser/task_manager/task_manager.h"
 #include "chrome/browser/ui/view_ids.h"
 #include "components/autofill/core/browser/autofill_ie_toolbar_import_win.h"
+#include "ui/base/touch/touch_device.h"
 #include "ui/base/win/shell.h"
 #endif  // OS_WIN
 
@@ -1127,7 +1128,22 @@ void Browser::TabStripEmpty() {
 }
 
 bool Browser::CanOverscrollContent() const {
-#if defined(USE_AURA)
+#if defined(OS_WIN)
+  // Don't enable overscroll on Windows machines unless they have a touch
+  // screen as these machines typically don't have a touchpad capable of
+  // horizontal scrolling. We are purposefully biased towards "no" here,
+  // so that we don't waste resources capturing screenshots for horizontal
+  // overscroll navigation unnecessarily.
+  bool allow_overscroll = ui::IsTouchDevicePresent();
+#elif defined(USE_AURA)
+  bool allow_overscroll = true;
+#else
+  bool allow_overscroll = false;
+#endif
+
+  if (!allow_overscroll)
+    return false;
+
   const std::string value = CommandLine::ForCurrentProcess()->
       GetSwitchValueASCII(switches::kOverscrollHistoryNavigation);
   bool overscroll_enabled = value != "0";
@@ -1143,9 +1159,6 @@ bool Browser::CanOverscrollContent() const {
   if (value == "1" && bookmark_bar_state_ == BookmarkBar::DETACHED)
     return false;
   return true;
-#else
-  return false;
-#endif
 }
 
 bool Browser::ShouldPreserveAbortedURLs(WebContents* source) {