Adds support for calling postMessage on a frame living in a different renderer.

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 2aba4bcb91a3ec52f4d25e195000466ec695f8ed..24736a459074a496535d03a91fd1bde96098f668 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -2418,6 +2418,47 @@ void WebContentsImpl::RouteCloseEvent(RenderViewHost* rvh) {
     GetRenderViewHost()->ClosePage();
 }
 
+void WebContentsImpl::RouteMessageEvent(
+    RenderViewHost* rvh,
+    const ViewHostMsg_PostMessage_Params& params) {
+  // Deliver the message to the active RenderViewHost, as long as the request
+  // came from a RenderViewHost in the same BrowsingInstance.
+  if (rvh->GetSiteInstance()->IsRelatedSiteInstance(GetSiteInstance())) {
+    ViewHostMsg_PostMessage_Params new_params(params);
+
+    // If there is a source_routing_id, translate it to the routing ID for
+    // the equivalent swapped out RVH in the target process.  If we need
+    // to create a swapped out RVH for the source tab, we create its opener
+    // chain as well, since those will also be accessible to the target page.
+    if (new_params.source_routing_id != MSG_ROUTING_NONE) {
+      // Try to look up the WebContents for the source page.
+      WebContentsImpl* source_contents = NULL;
+      RenderViewHostImpl* source_rvh = RenderViewHostImpl::FromID(
+          rvh->GetProcess()->GetID(), params.source_routing_id);
+      RenderViewHostDelegate* source_delegate =
+          source_rvh ? source_rvh->GetDelegate() : NULL;
+      if (source_delegate && source_delegate->GetRenderViewType() ==
+              content::VIEW_TYPE_WEB_CONTENTS) {
+        source_contents = static_cast<WebContentsImpl*>(source_delegate);
+      }
+
+      if (source_contents) {
+        new_params.source_routing_id =
+            source_contents->CreateOpenerRenderViews(GetSiteInstance());
+      } else {
+        // We couldn't find it, so don't pass a source frame.
+        new_params.source_routing_id = MSG_ROUTING_NONE;
+      }
+    }
+
+    // In most cases, we receive this from a swapped out RenderViewHost.
+    // It is possible to receive it from one that has just been swapped in,
+    // in which case we might as well deliver the message anyway.
+    GetRenderViewHost()->Send(new ViewMsg_PostMessageEvent(
+        GetRenderViewHost()->GetRoutingID(), new_params));
+  }
+}
+
 void WebContentsImpl::RunJavaScriptMessage(
     RenderViewHost* rvh,
     const string16& message,