Start caching the theme color in web_contents

content/public/browser/web_contents.h

Index: content/public/browser/web_contents.h
diff --git a/content/public/browser/web_contents.h b/content/public/browser/web_contents.h
index 493abd8f0d4b297b307c45e5a0890ffe5a806b41..40850b2521191e3ca69b6434d7213f2d6ea9e233 100644
--- a/content/public/browser/web_contents.h
+++ b/content/public/browser/web_contents.h
@@ -224,6 +224,10 @@ class WebContents : public PageNavigator,
   // nullptr.
   virtual RenderWidgetHostView* GetFullscreenRenderWidgetHostView() const = 0;
 
+  // Returns the theme color for the underlying content as set by the
+  // theme-color meta tag.
+  virtual SkColor GetThemeColor() const = 0;
+
   // Create a WebUI page for the given url. In most cases, this doesn't need to
   // be called by embedders since content will create its own WebUI objects as
   // necessary. However if the embedder wants to create its own WebUI object and