Implement sequential focus navigation for OOPIF.

content/common/frame_messages.h

Index: content/common/frame_messages.h
diff --git a/content/common/frame_messages.h b/content/common/frame_messages.h
index f4fc8b5b1e3bbe4eca185a760961e2e0d1bd0e88..bf87e01623f647ab7a11483081149ce9229352f2 100644
--- a/content/common/frame_messages.h
+++ b/content/common/frame_messages.h
@@ -29,6 +29,7 @@
 #include "content/public/common/three_d_api_types.h"
 #include "content/public/common/transition_element.h"
 #include "ipc/ipc_message_macros.h"
+#include "third_party/WebKit/public/platform/WebFocusType.h"
 #include "third_party/WebKit/public/web/WebFrameOwnerProperties.h"
 #include "third_party/WebKit/public/web/WebTreeScopeType.h"
 #include "ui/gfx/ipc/gfx_param_traits.h"
@@ -720,6 +721,14 @@ IPC_MESSAGE_ROUTED3(FrameMsg_GetSerializedHtmlWithLocalLinks,
 IPC_MESSAGE_ROUTED1(FrameMsg_SetFrameOwnerProperties,
                     blink::WebFrameOwnerProperties /* frame_owner_properties */)
 
+// Request to continue running the sequential focus navigation algorithm in
+// this frame.  |source_routing_id| identifies the frame that issued this
+// request.  This message is sent when pressing <tab> or <shift-tab> needs to
+// find the next focusable element in a cross-process frame.
+IPC_MESSAGE_ROUTED2(FrameMsg_AdvanceFocus,
+                    blink::WebFocusType /* type */,
+                    int /* source_routing_id */)
+
 #if defined(ENABLE_PLUGINS)
 // Notifies the renderer of updates to the Plugin Power Saver origin whitelist.
 IPC_MESSAGE_ROUTED1(FrameMsg_UpdatePluginContentOriginWhitelist,
@@ -1250,6 +1259,15 @@ IPC_MESSAGE_ROUTED2(FrameHostMsg_SerializedHtmlWithLocalLinksResponse,
 IPC_MESSAGE_ROUTED1(FrameHostMsg_UpdatePageImportanceSignals,
                     content::PageImportanceSignals)
 
+// This message is sent from a RenderFrameProxy when sequential focus
+// navigation needs to advance into its actual frame.  |source_routing_id|
+// identifies the frame that issued this request.  This is used when pressing
+// <tab> or <shift-tab> hits an out-of-process iframe when searching for the
+// next focusable element.
+IPC_MESSAGE_ROUTED2(FrameHostMsg_AdvanceFocus,
+                    blink::WebFocusType /* type */,
+                    int /* source_routing_id */)
+
 #if defined(OS_MACOSX) || defined(OS_ANDROID)
 
 // Message to show/hide a popup menu using native controls.