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

third_party/WebKit/Source/web/InspectorEmulationAgent.h

Index: third_party/WebKit/Source/web/InspectorEmulationAgent.h
diff --git a/third_party/WebKit/Source/web/InspectorEmulationAgent.h b/third_party/WebKit/Source/web/InspectorEmulationAgent.h
index ae6ea0a1616bbab9dcdb7a20974391b9f589ad5c..7b74f274dbac859bc3489de7094e5e39447920d3 100644
--- a/third_party/WebKit/Source/web/InspectorEmulationAgent.h
+++ b/third_party/WebKit/Source/web/InspectorEmulationAgent.h
@@ -14,6 +14,12 @@ namespace blink {
 class WebLocalFrameImpl;
 class WebViewImpl;
 
+namespace protocol {
+namespace DOM {
+class RGBA;
+}  // namespace DOM
+}  // namespace protocol
+
 class InspectorEmulationAgent final
     : public InspectorBaseAgent<protocol::Emulation::Metainfo> {
   WTF_MAKE_NONCOPYABLE(InspectorEmulationAgent);
@@ -41,6 +47,8 @@ class InspectorEmulationAgent final
   Response setCPUThrottlingRate(double) override;
   Response setVirtualTimePolicy(const String& policy,
                                 Maybe<int> virtualTimeBudgetMs) override;
+  Response setDefaultBackgroundColor(
+      std::unique_ptr<protocol::DOM::RGBA>) override;
 
   // InspectorBaseAgent overrides.
   Response disable() override;