For Desktop tab sharing, activate selected inactive tab

chrome/browser/ui/views/desktop_media_picker_views.cc

Index: chrome/browser/ui/views/desktop_media_picker_views.cc
diff --git a/chrome/browser/ui/views/desktop_media_picker_views.cc b/chrome/browser/ui/views/desktop_media_picker_views.cc
index cfa7b0ffbbe4a85ea0d2552298547c8f7894edab..8bc5fc08bab122b8533349939cbd02195bedb18c 100644
--- a/chrome/browser/ui/views/desktop_media_picker_views.cc
+++ b/chrome/browser/ui/views/desktop_media_picker_views.cc
@@ -18,6 +18,7 @@
 #include "components/constrained_window/constrained_window_views.h"
 #include "components/web_modal/web_contents_modal_dialog_manager.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/web_contents_delegate.h"
 #include "grit/components_strings.h"
 #include "ui/aura/window_tree_host.h"
@@ -514,15 +515,25 @@ bool DesktopMediaPickerDialogView::Accept() {
 
   // Ok button should only be enabled when a source is selected.
   DCHECK(selection);
-
-  DesktopMediaID source;
-  if (selection)
-    source = selection->source_id();
-
+  DesktopMediaID source = selection->source_id();
   source.audio_share = audio_share_checkbox_ &&
                        audio_share_checkbox_->enabled() &&
                        audio_share_checkbox_->checked();
 
+  // If the media source is an tab, activate it.
+  if (source.type == DesktopMediaID::TYPE_WEB_CONTENTS) {
+    content::RenderFrameHost* render_frame_host =
+        content::RenderFrameHost::FromID(
+            source.web_contents_id.render_process_id,
+            source.web_contents_id.main_render_frame_id);
+    if (render_frame_host) {

[msw, 2016/03/16 00:38:06]

nit: FromRenderFrameHost can take a nullptr, inline the
content::RenderFrameHost::FromID call, as you had in the prior patch set, or at
least remove this check.

+      content::WebContents* tab =
+          content::WebContents::FromRenderFrameHost(render_frame_host);
+      if (tab)
+        tab->GetDelegate()->ActivateContents(tab);
+    }
+  }
+
   if (parent_)
     parent_->NotifyDialogResult(source);