touchui: support XInput2 MT

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 0a8d7ba9cb72ad0a742ffbc23ad824bc54f6630d..43d7470f0857d954ff208768496046b460f14baa 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -214,6 +214,9 @@
       # Webrtc compilation is enabled by default. Set to 0 to disable.
       'enable_webrtc%': 1,
 
+      # XInput2 multitouch support is disabled by default.
+      'use_xi2_mt%': 0,
+
       'conditions': [
         # Use Skia as WebKit renderer on Mac
         ['OS=="mac"', {
@@ -305,6 +308,7 @@
     'enable_flapper_hacks%': '<(enable_flapper_hacks)',
     'chromeos%': '<(chromeos)',
     'touchui%': '<(touchui)',
+    'use_xi2_mt%':'<(use_xi2_mt)',
     'webui_dialogs%': '<(webui_dialogs)',
     'file_manager_extension%': '<(file_manager_extension)',
     'webui_task_manager%': '<(webui_task_manager)',
@@ -800,6 +804,9 @@
       ['touchui==1', {
         'defines': ['TOUCH_UI=1'],
       }],
+      ['use_xi2_mt==1', {
+        'defines': ['USE_XI2_MT=1'],

[Daniel Kurtz, 2011/09/20 05:12:27]

Here, could you set USE_XI2_MT equal to the required XI2 minor minimum version? 
Is there any precedence for non-boolean define values?

[ningxin.hu, 2011/09/20 14:28:59]

Good idea! Will implement it.

+      }],
       ['use_wayland==1', {
         'defines': ['USE_WAYLAND=1', 'WL_EGL_PLATFORM=1'],
       }],