[devtools] Add a command to emulate the default background color.

third_party/WebKit/Source/web/WebViewImpl.h

Index: third_party/WebKit/Source/web/WebViewImpl.h
diff --git a/third_party/WebKit/Source/web/WebViewImpl.h b/third_party/WebKit/Source/web/WebViewImpl.h
index e88da4c0266c6c9956514d5a7747517faa980cc8..b69faa92ecd17eaa404bd293755f2c00ec38a96e 100644
--- a/third_party/WebKit/Source/web/WebViewImpl.h
+++ b/third_party/WebKit/Source/web/WebViewImpl.h
@@ -286,14 +286,14 @@ class WEB_EXPORT WebViewImpl final
   void invalidateRect(const IntRect&);
 
   void setBaseBackgroundColor(WebColor);
+  void setBaseBackgroundColorOverride(WebColor);
   void setBackgroundColorOverride(WebColor);
   void setZoomFactorOverride(float);
   void setCompositorDeviceScaleFactorOverride(float);
   void setDeviceEmulationTransform(const TransformationMatrix&);
   TransformationMatrix getDeviceEmulationTransformForTesting() const;
 
-  Color baseBackgroundColor() const { return m_baseBackgroundColor; }
-
+  Color baseBackgroundColor() const;
   WebColor backgroundColorOverride() const { return m_backgroundColorOverride; }
 
   Frame* focusedCoreFrame() const;
@@ -532,6 +532,8 @@ class WEB_EXPORT WebViewImpl final
   bool getCompositionCharacterBounds(WebVector<WebRect>&) override;
   void applyReplacementRange(const WebRange&) override;
 
+  void updateBaseBackgroundColor();
+
   friend class WebView;  // So WebView::Create can call our constructor
   friend class WebViewFrameWidget;
   friend class WTF::RefCounted<WebViewImpl>;
@@ -706,6 +708,7 @@ class WEB_EXPORT WebViewImpl final
   std::unique_ptr<FullscreenController> m_fullscreenController;
 
   WebColor m_baseBackgroundColor;
+  WebColor m_baseBackgroundColorOverride;
   WebColor m_backgroundColorOverride;
   float m_zoomFactorOverride;