Expose UkmService to content/

content/browser/renderer_host/render_widget_host_delegate.h

Index: content/browser/renderer_host/render_widget_host_delegate.h
diff --git a/content/browser/renderer_host/render_widget_host_delegate.h b/content/browser/renderer_host/render_widget_host_delegate.h
index a2d2d9bcfe55b03617deab88d9a8c5a6ea9a36dd..714041f59f18171ec03fde0af159355cf5d11ed1 100644
--- a/content/browser/renderer_host/render_widget_host_delegate.h
+++ b/content/browser/renderer_host/render_widget_host_delegate.h
@@ -32,6 +32,10 @@ namespace rappor {
 class Sample;
 }
 
+namespace ukm {
+class UkmService;
+}
+
 namespace content {
 
 class BrowserAccessibilityManager;
@@ -240,6 +244,11 @@ class CONTENT_EXPORT RenderWidgetHostDelegate {
   // if the eTLD+1 is not known for |render_widget_host|.
   virtual bool AddDomainInfoToRapporSample(rappor::Sample* sample);
 
+  // Update UkmService for the given source with the URL. Returns false

[Charlie Reis, 2017/05/24 16:28:32]

Can you elaborate what UkmService is here?  I didn't know it was URL-keyed
metrics until I dug into the code.

[Navid Zolghadr, 2017/05/25 15:45:46]

Done.

+  // if the Utl is not known for |render_widget_host|.

[Charlie Reis, 2017/05/24 16:28:32]

What is Utl?

[Navid Zolghadr, 2017/05/25 15:45:46]

Done.

+  virtual bool UpdateUrlForUkmSource(ukm::UkmService* service,

[Charlie Reis, 2017/05/24 16:28:32]

This doesn't look like it ever returns false in practice, and the proposed call
site in RenderWidgetHostLatencyTracker::GetUkmSourceId() (in
https://codereview.chromium.org/2888153002) doesn't check the return value. 
Maybe it should just be void?

[Navid Zolghadr, 2017/05/25 15:45:46]

Done.

+                                     int32_t ukm_source_id);
+
   // Notifies the delegate that a focused editable element has been touched
   // inside this RenderWidgetHost. If |editable| is true then the focused
   // element accepts text input.