Chromium side of maxTouchPoints implementation.

content/browser/web_contents/web_contents_impl.cc

 // Copyright (c) 2012 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 "content/browser/web_contents/web_contents_impl.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 583 matching lines @@
       switches::kDisableGestureRequirementForMediaFullscreen);
 #endif
 
   prefs.touch_enabled = ui::AreTouchEventsEnabled();
   prefs.device_supports_touch = prefs.touch_enabled &&
       ui::IsTouchDevicePresent();
 #if defined(OS_ANDROID)
   prefs.device_supports_mouse = false;
 #endif
 
+  prefs.pointer_events_max_touch_points_enabled = prefs.touch_enabled &&

[Rick Byers, 2013/10/10 22:42:40]

I don't think you want to look at touch_enabled here.  If touch isn't enabled,
then the API should return 0 not undefined, right?  At least I assume that's
what IE does.

[Rick Byers, 2013/10/10 22:42:40]

Does this override the status=experimental property in
RuntimeEnabledFeatures.in?  I.e. does this cause the API to be exposed even when
we're not running with --enable-experimental-web-platform-features?  I don't
think we want that - let's get it right as experimental, then launch it to all
users by flipping it to stable in a future CL.

If we're going to land support for all platforms before it goes stable (which I
think we can do), then you can just avoid having a pref for this entirely. 
We'll just flip it to stable once all the platforms that support touch supply
some value and then have no need to disable it in some cases.

+      ui::CanDetectMaxTouchPoints();
+  prefs.pointer_events_max_touch_points = ui::MaxTouchPoints();
+
    prefs.touch_adjustment_enabled =
        !command_line.HasSwitch(switches::kDisableTouchAdjustment);
    prefs.compositor_touch_hit_testing =
        !command_line.HasSwitch(cc::switches::kDisableCompositorTouchHitTesting);
 
 #if defined(OS_MACOSX) || defined(OS_CHROMEOS)
   bool default_enable_scroll_animator = true;
 #else
   bool default_enable_scroll_animator = false;
 #endif
@@ skipping 3220 matching lines @@
 }
 
 void WebContentsImpl::OnFrameRemoved(
     RenderViewHostImpl* render_view_host,
     int64 frame_id) {
    FOR_EACH_OBSERVER(WebContentsObserver, observers_,
                      FrameDetached(render_view_host, frame_id));
 }
 
 }  // namespace content