Allow vibrate in cross-origin iframes with user gesture.

third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp

Index: third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp
diff --git a/third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp b/third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp
index 77c0ce17a2369290356d15bd872b5cb3c38f69a3..befe390e8bee990f95f146aa90670853012d6f07 100644
--- a/third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp
+++ b/third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp
@@ -80,17 +80,21 @@ bool NavigatorVibration::vibrate(Navigator& navigator,
     return false;
 
   // TODO(lunalu): When FeaturePolicy is ready, take out the check for the
-  // runtime flag.
-  if (!isFeatureEnabledInFrame(blink::kVibrateFeature, frame)) {
-    if (RuntimeEnabledFeatures::featurePolicyEnabled()) {
-      frame->domWindow()->printErrorMessage(
-          "Navigator.vibrate() is not enabled in feature policy for this "
-          "frame.");
-    } else {
-      frame->domWindow()->printErrorMessage(
-          "A call of navigator.vibrate will be no-op inside cross-origin "
-          "iframes: https://www.chromestatus.com/feature/5682658461876224.");
-    }
+  // runtime flag. Please pay attention to the user gesture code below.
+  if (RuntimeEnabledFeatures::featurePolicyEnabled() &&

[iclelland, 2017/01/23 16:11:38]

This version of the logic lgtm, thanks!

I'll clean this up some once we resolve the other issues around feature policy
and default heuristics, but this looks like a good solution in the interim.

[Bin Lu, 2017/01/23 20:18:40]

Acknowledged.

+      !isFeatureEnabledInFrame(blink::kVibrateFeature, frame)) {
+    frame->domWindow()->printErrorMessage(
+        "Navigator.vibrate() is not enabled in feature policy for this "
+        "frame.");
+    return false;
+  }
+
+  if (!RuntimeEnabledFeatures::featurePolicyEnabled() &&
+      frame->isCrossOriginSubframe() && !frame->hasReceivedUserGesture()) {
+    frame->domWindow()->printErrorMessage(
+        "A call of navigator.vibrate will be no-op inside a cross-origin "
+        "iframe if there is no user activation on the iframe: "

[Rick Byers, 2017/01/23 15:42:14]

nit to wording - this sounds like a warning about a pending change.  How about:
"Blocked call to navigator.vibrate inside a cross-origin iframe because the
frame has never been activated by the user".

[Bin Lu, 2017/01/23 20:18:40]

Done.

+        "https://www.chromestatus.com/feature/5682658461876224.");
     return false;
   }