Set background color when adding a new tab.

chrome/browser/ui/browser.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/browser.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <string>
@@ skipping 1022 matching lines @@
   window_->GetLocationBar()->SaveStateToContents(contents);
 
   if (instant_controller_)
     instant_controller_->TabDeactivated(contents);
 }
 
 void Browser::ActiveTabChanged(WebContents* old_contents,
                                WebContents* new_contents,
                                int index,
                                int reason) {
+  // Copies the background color from an old WebContents to a new one that
+  // replaces it on the screen. This allows the new WebContents to use the
+  // old one's background color as the starting background color, before having
+  // loaded any contents. As a result, we avoid flashing white when moving to
+  // a new tab. (There is also code in RenderFrameHostManager to do something
+  // similar for intra-tab navigations.)
+  if (old_contents && new_contents) {
+    RenderWidgetHostView* old_view = old_contents->GetMainFrame()->GetView();

[Peter Kasting, 2017/03/09 00:02:03]

NIt: Document the null check, e.g. "While GetMainFrame() is guaranteed to return
non-null, GetView() is not, e.g. between WebContents creation and creation of
the RenderWidgetHostView."

[chrishtr, 2017/03/09 00:04:53]

Done.

+    RenderWidgetHostView* new_view = new_contents->GetMainFrame()->GetView();
+    if (old_view && new_view)
+      new_view->SetBackgroundColor(old_view->background_color());
+  }
+
   content::RecordAction(UserMetricsAction("ActiveTabChanged"));
 
   // Update the bookmark state, since the BrowserWindow may query it during
   // OnActiveTabChanged() below.
   UpdateBookmarkBarState(BOOKMARK_BAR_STATE_CHANGE_TAB_SWITCH);
 
   // Let the BrowserWindow do its handling.  On e.g. views this changes the
   // focused object, which should happen before we update the toolbar below,
   // since the omnibox expects the correct element to already be focused when it
   // is updated.
@@ skipping 1609 matching lines @@
     // new window later, thus we need to navigate the window now.
     if (contents) {
       contents->web_contents()->GetController().LoadURL(
           target_url, content::Referrer(), ui::PAGE_TRANSITION_LINK,
           std::string());  // No extra headers.
     }
   }
 
   return contents != NULL;
 }