Introduce content::RenderWidgetHostViewPort (in content/port/browser).

content/content_browser.gypi

Index: content/content_browser.gypi
diff --git a/content/content_browser.gypi b/content/content_browser.gypi
index d9c32bffb87d6a0d1def4fc40aa055cea40a820b..6bbed30b2b78cc473e0a0649d504d299182ef947 100644
--- a/content/content_browser.gypi
+++ b/content/content_browser.gypi
@@ -26,6 +26,8 @@
     '<(INTERMEDIATE_DIR)',
   ],
   'sources': [
+    'port/browser/render_widget_host_view_port.cc',
+    'port/browser/render_widget_host_view_port.h',
     'public/browser/access_token_store.h',
     'public/browser/browser_child_process_host.h',
     'public/browser/browser_child_process_host_delegate.cc',
@@ -91,6 +93,8 @@
     'public/browser/render_view_host_delegate.h',
     'public/browser/render_view_host_observer.cc',
     'public/browser/render_view_host_observer.h',
+    'public/browser/render_widget_host_view.cc',
+    'public/browser/render_widget_host_view.h',
     'public/browser/render_widget_host_view_mac_delegate.h',
     'public/browser/resource_context.h',
     'public/browser/resource_dispatcher_host_delegate.cc',
@@ -536,8 +540,8 @@
     'browser/renderer_host/render_widget_host.h',
     'browser/renderer_host/render_widget_host_gtk.cc',
     'browser/renderer_host/render_widget_host_mac.cc',
-    'browser/renderer_host/render_widget_host_view.cc',
-    'browser/renderer_host/render_widget_host_view.h',
+    'browser/renderer_host/render_widget_host_view_base.cc',
+    'browser/renderer_host/render_widget_host_view_base.h',
     'browser/renderer_host/render_widget_host_view_android.cc',
     'browser/renderer_host/render_widget_host_view_aura.cc',
     'browser/renderer_host/render_widget_host_view_aura.h',