Exposes the UKM source ID in WebContentsImpl to WebContents.

Exposes the UKM source ID from WebContentsImpl to WebContents,
so it can be used in NavigationPredictor to send metrics to the
UKM.

Bug: 972128
Change-Id: I7181890ed7977904b8d4dca9db78b7bbbad85b83
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1686633
Reviewed-by: Steven Holte <[email protected]>
Reviewed-by: Kinuko Yasuda <[email protected]>
Reviewed-by: Tarun Bansal <[email protected]>
Reviewed-by: Ryan Sturm <[email protected]>
Commit-Queue: Sofiya Semenova <[email protected]>
Cr-Commit-Position: refs/heads/master@{#676267}
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 3cc697a..4f1cac5 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -6725,6 +6725,10 @@
   return GetAudioStreamFactory()->group_id();
 }
 
+ukm::SourceId WebContentsImpl::GetLastCommittedSourceId() {
+  return last_committed_source_id_;
+}
+
 BrowserPluginEmbedder* WebContentsImpl::GetBrowserPluginEmbedder() const {
   return browser_plugin_embedder_.get();
 }