Set background color when adding a new tab.

chrome/browser/ui/browser.cc

Index: chrome/browser/ui/browser.cc
diff --git a/chrome/browser/ui/browser.cc b/chrome/browser/ui/browser.cc
index d2063c2f561ca8edecea3ef93c812f62903d6b41..d9f656944e700b18ef45a1f80866a9184ec24f87 100644
--- a/chrome/browser/ui/browser.cc
+++ b/chrome/browser/ui/browser.cc
@@ -1040,6 +1040,19 @@ 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