Extract minimal RenderViewHost interface for embedders, leaving

chrome/browser/ui/cocoa/extensions/extension_view_mac.mm

Index: chrome/browser/ui/cocoa/extensions/extension_view_mac.mm
diff --git a/chrome/browser/ui/cocoa/extensions/extension_view_mac.mm b/chrome/browser/ui/cocoa/extensions/extension_view_mac.mm
index 17b2c5887fe79d6b775f9dc0da29a8b6e5f65aea..0c02beed51e745d108c03905f485dae8c964f311 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_view_mac.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_view_mac.mm
@@ -48,8 +48,8 @@ void ExtensionViewMac::DidStopLoading() {
 }
 
 void ExtensionViewMac::SetBackground(const SkBitmap& background) {
-  if (!pending_background_.empty() && render_view_host()->view()) {
-    render_view_host()->view()->SetBackground(background);
+  if (!pending_background_.empty() && render_view_host()->GetView()) {
+    render_view_host()->GetView()->SetBackground(background);
   } else {
     pending_background_ = background;
   }
@@ -70,15 +70,15 @@ void ExtensionViewMac::RenderViewCreated() {
       CGSizeMake(ExtensionViewMac::kMaxWidth, ExtensionViewMac::kMaxHeight));
   extension_host_->DisableScrollbarsForSmallWindows(largest_popup_size);
 
-  if (!pending_background_.empty() && render_view_host()->view()) {
-    render_view_host()->view()->SetBackground(pending_background_);
+  if (!pending_background_.empty() && render_view_host()->GetView()) {
+    render_view_host()->GetView()->SetBackground(pending_background_);
     pending_background_.reset();
   }
 }
 
 void ExtensionViewMac::WindowFrameChanged() {
-  if (render_view_host()->view())
-    render_view_host()->view()->WindowFrameChanged();
+  if (render_view_host()->GetView())
+    render_view_host()->GetView()->WindowFrameChanged();
 }
 
 void ExtensionViewMac::CreateWidgetHostView() {