Add a feature which, when enabled, blocks permissions after X prompt dismissals.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 7dd4a3842746ee713a6c2e134eb3d2656a10f118..8bb46f742773a0c9eb459323f2c27519894a87e0 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -39505,6 +39505,28 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Permissions.Prompt.DismissCount">
+  <owner>dominickn@chromium.org</owner>
+  <summary>
+    This metric, recorded at the time of a permission prompt dismissal, records
+    the total number of prompt dismissal events for this origin, inclusive of

[Ilya Sherman, 2016/08/08 20:04:56]

Is this the total number across all of time?  Or over the last N months?  That
is, does the dismissal data ever expire?

[dominickn, 2016/08/09 08:31:24]

The dismissal data never expires - though it will be reset if the user clears
their browsing data. I'll clarify.

+    the current dismissal. Every event in a bucket larger than 1 in this
+    histogram will also have an event in each smaller bucket. The suffix of the
+    histogram indicates which particular permission.
+  </summary>
+</histogram>
+
+<histogram name="Permissions.Prompt.IgnoreCount">
+  <owner>dominickn@chromium.org</owner>
+  <summary>
+    This metric, recorded at the time of a permission prompt ignore, records the
+    total number of prompt ignore events for this origin, inclusive of the
+    current ignore. Every event in a bucket larger than 1 in this histogram will
+    also have an event in each smaller bucket. The suffix of the histogram
+    indicates which particular permission.
+  </summary>
+</histogram>
+
 <histogram name="Permissions.Prompt.MergedBubbleAccepted"
     enum="PermissionRequestType">
   <owner>benwells@chromium.org</owner>
@@ -100484,6 +100506,8 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="Permissions.Action"/>
   <affected-histogram name="Permissions.Action.InsecureOrigin"/>
   <affected-histogram name="Permissions.Action.SecureOrigin"/>
+  <affected-histogram name="Permissions.Prompt.DismissCount"/>
+  <affected-histogram name="Permissions.Prompt.IgnoreCount"/>
   <affected-histogram name="Permissions.Requested.CrossOrigin"/>
 </histogram_suffixes>