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

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
===================================================================
--- chrome/browser/about_flags.cc	(revision 134559)
+++ chrome/browser/about_flags.cc	(working copy)
@@ -678,6 +678,15 @@
     kOsAll,
     SINGLE_VALUE_TYPE_AND_VALUE(switches::kAllowNaClSocketAPI, "*")
   },
+#if defined(OS_CHROMEOS)
+  {
+    "allow-touchpad-three-finger-click",
+    IDS_FLAGS_ALLOW_TOUCHPAD_THREE_FINGER_CLICK_NAME,
+    IDS_FLAGS_ALLOW_TOUCHPAD_THREE_FINGER_CLICK_DESCRIPTION,
+    kOsCrOS,
+    SINGLE_VALUE_TYPE(switches::kEnableTouchpadThreeFingerClick)
+  },
+#endif
 };
 
 const Experiment* experiments = kExperiments;