Add UMA metric for "View Original" link clicks in distilled page viewer.

components/dom_distiller/content/dom_distiller_viewer_source.cc

Index: components/dom_distiller/content/dom_distiller_viewer_source.cc
diff --git a/components/dom_distiller/content/dom_distiller_viewer_source.cc b/components/dom_distiller/content/dom_distiller_viewer_source.cc
index 3d26eb889426306f885df9b1b1dd52c839bf7873..ed51c47c83ceb4f5af9747c81dd8b545f918aa59 100644
--- a/components/dom_distiller/content/dom_distiller_viewer_source.cc
+++ b/components/dom_distiller/content/dom_distiller_viewer_source.cc
@@ -11,6 +11,7 @@
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/user_metrics.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/dom_distiller/core/distilled_page_prefs.h"
 #include "components/dom_distiller/core/dom_distiller_service.h"
@@ -21,6 +22,7 @@
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_view_host.h"
+#include "content/public/browser/user_metrics.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "net/base/url_util.h"
@@ -284,6 +286,11 @@ void DomDistillerViewerSource::StartDataRequest(
     callback.Run(base::RefCountedString::TakeString(&js));
     return;
   }
+  if (kViewerViewOriginalPath == path) {
+    content::RecordAction(base::UserMetricsAction("DomDistiller_ViewOriginal"));

[nyquist, 2014/08/25 01:13:03]

Would this ever be needed on iOS? I.e., should it live in viewer.[cc|h]?
I'm guessing it's easier to just copy-paste this string if that's the case?

[Yaron, 2014/08/25 19:41:23]

I think this is simple enough to leave.

+    callback.Run(NULL);
+    return;
+  }
   content::WebContents* web_contents =
       content::WebContents::FromRenderFrameHost(
           content::RenderFrameHost::FromID(render_process_id,