Update First Paint to include paint of non-default document background color

third_party/WebKit/Source/core/paint/ViewPainter.cpp

 // Copyright 2014 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 "core/paint/ViewPainter.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutView.h"
@@ skipping 149 matching lines @@
           backgroundRect, baseBackgroundColor,
           shouldClearCanvas ? SkBlendMode::kSrc : SkBlendMode::kSrcOver);
     }
     context.beginLayer();
   }
 
   Color combinedBackgroundColor =
       shouldDrawBackgroundInSeparateBuffer
           ? rootBackgroundColor
           : baseBackgroundColor.blend(rootBackgroundColor);
+  if (combinedBackgroundColor != frameView.baseBackgroundColor() &&
+      !context.getPaintController().nonDefaultBackgroundColorPainted()) {
+    TRACE_EVENT_INSTANT0("blink.user_timing", "paintNonDefaultBackgroundColor",
+                         TRACE_EVENT_SCOPE_GLOBAL);
+    context.getPaintController().setNonDefaultBackgroundColorPainted();
+  }
   if (combinedBackgroundColor.alpha()) {
     if (!combinedBackgroundColor.hasAlpha() &&
         RuntimeEnabledFeatures::slimmingPaintV2Enabled())
       recorder.setKnownToBeOpaque();
     context.fillRect(backgroundRect, combinedBackgroundColor,
                      (shouldDrawBackgroundInSeparateBuffer || shouldClearCanvas)
                          ? SkBlendMode::kSrc
                          : SkBlendMode::kSrcOver);
   } else if (shouldClearCanvas && !shouldDrawBackgroundInSeparateBuffer) {
     context.fillRect(backgroundRect, Color(), SkBlendMode::kClear);
@@ skipping 18 matching lines @@
                                  LayoutRect(paintRect), BackgroundBleedNone);
       context.restore();
     }
   }
 
   if (shouldDrawBackgroundInSeparateBuffer)
     context.endLayer();
 }
 
 }  // namespace blink