Initial work on a new <view> element backed by a mojo::View.

sky/engine/core/loader/FrameLoaderClient.h

Index: sky/engine/core/loader/FrameLoaderClient.h
diff --git a/sky/engine/core/loader/FrameLoaderClient.h b/sky/engine/core/loader/FrameLoaderClient.h
index dd9c9e7afcb8b0f620dcef379f249c86aac942f6..df721125bfb7db0668cb037da03540d1b60eccb3 100644
--- a/sky/engine/core/loader/FrameLoaderClient.h
+++ b/sky/engine/core/loader/FrameLoaderClient.h
@@ -49,6 +49,7 @@ namespace blink {
     class FetchRequest;
     class FrameLoader;
     class FrameNetworkingContext;
+    class HTMLViewElement;
     class IntSize;
     class KURL;
     class LocalFrame;
@@ -87,6 +88,9 @@ namespace blink {
 
         virtual void loadURLExternally(const ResourceRequest&, NavigationPolicy, const String& suggestedName = String()) = 0;
 
+        // TODO(mpcomplete): return surface ID?
+        virtual void createView(const KURL&, HTMLViewElement*) = 0;
+
         // Transmits the change in the set of watched CSS selectors property
         // that match any element on the frame.
         virtual void selectorMatchChanged(const Vector<String>& addedSelectors, const Vector<String>& removedSelectors) = 0;