Chromium side of maxTouchPoints implementation.

Intent to implement-and-ship: https://groups.google.com/a/chromium.org/forum/#!searchin/blink-dev/maxTouchPoints/blink-dev/ayzxdztUlOQ/rd-z_Jo3ocIJ

navigator.maxTouchPoints is defined in the W3C Pointer Events
standard draft:
http://www.w3.org/TR/pointerevents/#widl-Navigator-maxTouchPoints

Depends on blink revision 160153:
https://src.chromium.org/viewvc/blink?view=revision&revision=160153

BUG=248918

Review URL: https://codereview.chromium.org/26764002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231203 0039d316-1c4b-4281-b951-d872f2087c98

AUTHORS

@@ -249,6 +249,7 @@ Sanjoy Pal <sanjoy.pal@samsung.com>
 Sanne Wouda <sanne.wouda@gmail.com>
 Sathish Kuppuswamy <sathish.kuppuswamy@intel.com>
 Satoshi Matsuzaki <satoshi.matsuzaki@gmail.com>
+Scott Blomquist <sblom@microsoft.com>
 Sean Bryant <sean@cyberwang.net>
 Seo Sanghyeon <sanxiyn@gmail.com>
 Seokju Kwon <seokju.kwon@gmail.com>

content/browser/web_contents/web_contents_impl.cc

@@ -611,10 +611,12 @@ WebPreferences WebContentsImpl::GetWebkitPrefs(RenderViewHost* rvh,
   prefs.device_supports_mouse = false;
 #endif
 
-   prefs.touch_adjustment_enabled =
-       !command_line.HasSwitch(switches::kDisableTouchAdjustment);
-   prefs.compositor_touch_hit_testing =
-       !command_line.HasSwitch(cc::switches::kDisableCompositorTouchHitTesting);
+  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;

content/public/common/common_param_traits_macros.h

@@ -160,6 +160,7 @@ IPC_STRUCT_TRAITS_BEGIN(WebPreferences)
   IPC_STRUCT_TRAITS_MEMBER(device_supports_touch)
   IPC_STRUCT_TRAITS_MEMBER(device_supports_mouse)
   IPC_STRUCT_TRAITS_MEMBER(touch_adjustment_enabled)
+  IPC_STRUCT_TRAITS_MEMBER(pointer_events_max_touch_points)
   IPC_STRUCT_TRAITS_MEMBER(fixed_position_creates_stacking_context)
   IPC_STRUCT_TRAITS_MEMBER(sync_xhr_in_documents_enabled)
   IPC_STRUCT_TRAITS_MEMBER(deferred_image_decoding_enabled)

content/renderer/web_preferences.cc

@@ -298,6 +298,7 @@ void ApplyWebPreferences(const WebPreferences& prefs, WebView* web_view) {
 
   WebRuntimeFeatures::enableLazyLayout(prefs.lazy_layout_enabled);
   WebRuntimeFeatures::enableTouch(prefs.touch_enabled);
+  settings->setMaxTouchPoints(prefs.pointer_events_max_touch_points);
   settings->setDeviceSupportsTouch(prefs.device_supports_touch);
   settings->setDeviceSupportsMouse(prefs.device_supports_mouse);
   settings->setEnableTouchAdjustment(prefs.touch_adjustment_enabled);

ui/base/touch/touch_device.cc

@@ -12,4 +12,8 @@ bool IsTouchDevicePresent() {
   return false;
 }
 
+int MaxTouchPoints() {
+  return 0;
+}
+
 }  // namespace ui

ui/base/touch/touch_device.h

@@ -9,9 +9,23 @@
 
 namespace ui {
 
+// TODO(sblom): This is non-standard, and should be removed before
+// RuntimeEnabledFlags::PointerEventsMaxTouchPoints is marked stable.
+// Tracked by: http://crbug.com/308649
+const int kMaxTouchPointsUnknown = -1;
+
 // Returns true if a touch device is available.
 UI_EXPORT bool IsTouchDevicePresent();
 
+// Returns the maximum number of simultaneous touch contacts supported
+// by the device. In the case of devices with multiple digitizers (e.g.
+// multiple touchscreens), the value MUST be the maximum of the set of
+// maximum supported contacts by each individual digitizer.
+// For example, suppose a device has 3 touchscreens, which support 2, 5,
+// and 10 simultaneous touch contacts, respectively. This returns 10.
+// http://www.w3.org/TR/pointerevents/#widl-Navigator-maxTouchPoints
+UI_EXPORT int MaxTouchPoints();
+
 }  // namespace ui
 
 #endif  // UI_BASE_TOUCH_TOUCH_DEVICE_H_

ui/base/touch/touch_device_android.cc

@@ -10,4 +10,17 @@ bool IsTouchDevicePresent() {
   return true;
 }
 
+// Looks like the best we can do here is detect 1, 2+, or 5+ by
+// feature detecting:
+// FEATURE_TOUCHSCREEN (1),
+// FEATURE_TOUCHSCREEN_MULTITOUCH (2),
+// FEATURE_TOUCHSCREEN_MULTITOUCH_DISTINCT (2+), or
+// FEATURE_TOUCHSCREEN_MULTITOUCH_JAZZHANDS (5+)
+//
+// Probably start from the biggest and detect down the list until we
+// find one that's supported and return its value.
+int MaxTouchPoints() {
+  return kMaxTouchPointsUnknown;
+}
+
 }  // namespace ui

ui/base/touch/touch_device_aurax11.cc

@@ -11,4 +11,8 @@ bool IsTouchDevicePresent() {
   return ui::TouchFactory::GetInstance()->IsTouchDevicePresent();
 }
 
+int MaxTouchPoints() {
+  return kMaxTouchPointsUnknown;
+}
+
 }  // namespace ui

ui/base/touch/touch_device_ozone.cc

@@ -11,4 +11,8 @@ bool IsTouchDevicePresent() {
   return true;
 }
 
+int MaxTouchPoints() {
+  return kMaxTouchPointsUnknown;
+}
+
 }  // namespace ui

ui/base/touch/touch_device_win.cc

@@ -14,4 +14,8 @@ bool IsTouchDevicePresent() {
       ((value & NID_INTEGRATED_TOUCH) || (value & NID_EXTERNAL_TOUCH));
 }
 
+int MaxTouchPoints() {
+  return GetSystemMetrics(SM_MAXIMUMTOUCHES);
+}
+
 }  // namespace ui

webkit/common/webpreferences.cc

@@ -90,6 +90,7 @@ WebPreferences::WebPreferences()
       device_supports_touch(false),
       device_supports_mouse(true),
       touch_adjustment_enabled(true),
+      pointer_events_max_touch_points(0),
       fixed_position_creates_stacking_context(false),
       sync_xhr_in_documents_enabled(true),
       deferred_image_decoding_enabled(false),

webkit/common/webpreferences.h

@@ -140,6 +140,7 @@ struct WEBKIT_COMMON_EXPORT WebPreferences {
   bool device_supports_touch;
   bool device_supports_mouse;
   bool touch_adjustment_enabled;
+  int pointer_events_max_touch_points;
   bool fixed_position_creates_stacking_context;
   bool sync_xhr_in_documents_enabled;
   bool deferred_image_decoding_enabled;