[Extensions] Add metrics for renderer sync IPCs performance

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 30cd03f55469e4aae9bbbb9efe85a856131ac662..f1d787070955114258855d5f02c174fc029cb863 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -15858,6 +15858,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>The manifest version of each loaded extension.</summary>
 </histogram>
 
+<histogram name="Extensions.Messaging.GetPortIdSyncTime" units="ms">
+  <owner>rdevlin.cronin@chromium.org</owner>
+  <summary>
+    The amount of synchronous time taken for the renderer to request an
+    extension message port id from the browser.

[Mark P, 2016/09/08 22:48:53]

nit: given that the function you're call in all these cases for this histogram
(and suffix friends) is ExtensionHostMsg_OpenChannelTo..., perhaps this
description should mention the word "channel" somewhere.  Maybe also the
histogram name should be revised.

[Devlin, 2016/09/08 23:04:22]

Adjusted the histogram description.  I think the name's probably okay, since
Port is the (slightly) more canonical reference to this, but let me know if you
disagree and I'll update it.

+  </summary>
+</histogram>
+
 <histogram name="Extensions.NetworkDelay" units="ms">
   <owner>battre@chromium.org</owner>
   <summary>Time that network requests were blocked due to extensions.</summary>
@@ -16567,6 +16575,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Extensions.SyncGetMessageBundle" units="ms">
+  <owner>rdevlin.cronin@chromium.org</owner>
+  <summary>
+    The amount of synchronous time spent retrieving an extension's message
+    bundle (the collection of its i18n resources) from the browser.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.ThrottledNetworkRequestDelay" units="ms">
   <owner>rdevlin.cronin@chromium.org</owner>
   <summary>
@@ -100380,6 +100396,13 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="Extensions.Functions.SucceededTime"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="ExtensionMessagingPortType" separator=".">
+  <suffix name="Extension" label="A port opened to an extension context."/>
+  <suffix name="NativeApp" label="A port opened to a native application."/>
+  <suffix name="Tab" label="A port opened to a tab context."/>
+  <affected-histogram name="Extensions.Messaging.GetPortIdSyncTime"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="ExtensionsDatabaseOpen" separator=".">
   <suffix name="Rules" label="Rules backing stores"/>
   <suffix name="Settings" label="Settings backing stores"/>