Remove navigator.vibrate without user gesture.

content/public/common/content_features.cc

Index: content/public/common/content_features.cc
diff --git a/content/public/common/content_features.cc b/content/public/common/content_features.cc
index 1436426c834edee4716410d64a9562265bcf5ca5..8124515522c1bb5c6b7a9564310d9a4d6f39cb49 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -226,6 +226,10 @@ const base::Feature kTokenBinding{"token-binding",
 const base::Feature kTouchpadAndWheelScrollLatching{
     "TouchpadAndWheelScrollLatching", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Controls whether vibrate requires user gesture.
+const base::Feature kVibrateRequiresUserGesture{
+    "VibrateRequiresUserGesture", base::FEATURE_ENABLED_BY_DEFAULT};

[ojan, 2017/04/14 00:52:43]

This isn't actually hooked up to the RuntimeEnabledFeature here I think. See
WebRuntimeFeatures.cpp and runtime_features.cc for examples of how to do the
plumbing.

[binlu, 2017/04/14 01:16:35]

Done. It's weird that the change was there before but dropped somehow during
various rebases:
https://codereview.chromium.org/2778693004/diff/60001/content/child/runtime_f...
just added it back: 
https://codereview.chromium.org/2778693004/diff/400001/content/child/runtime_...

+
 // Enables VR UI.
 const base::Feature kVrShell{"VrShell", base::FEATURE_DISABLED_BY_DEFAULT};