Support for cros touchpad 3-finger click as middle button.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
===================================================================
--- chrome/common/pref_names.cc	(revision 134766)
+++ chrome/common/pref_names.cc	(working copy)
@@ -452,6 +452,10 @@
 // A boolean pref set to true if touchpad tap-to-click is enabled.
 const char kTapToClickEnabled[] = "settings.touchpad.enable_tap_to_click";
 
+// A boolean pref set to true if touchpad three-finger-click is enabled.
+const char kEnableTouchpadThreeFingerClick[] =
+    "settings.touchpad.enable_three_finger_click";
+
 // A boolean pref set to true if touchpad natural scrolling is enabled.
 const char kNaturalScroll[] = "settings.touchpad.natural_scroll";