Add a warning for the deprecation of content-initiated data URL navigations

content/browser/frame_host/navigation_handle_impl.cc

Index: content/browser/frame_host/navigation_handle_impl.cc
diff --git a/content/browser/frame_host/navigation_handle_impl.cc b/content/browser/frame_host/navigation_handle_impl.cc
index 74e0b202c6f005ffc79bb32c909b01bb847c83f2..3ba4402a309983931c0075a25572992012e9d069 100644
--- a/content/browser/frame_host/navigation_handle_impl.cc
+++ b/content/browser/frame_host/navigation_handle_impl.cc
@@ -154,6 +154,14 @@ NavigationHandleImpl::~NavigationHandleImpl() {
         base::Bind(&NotifyAbandonedTransferNavigation, GetGlobalRequestID()));
   }
 
+  if (url_.SchemeIs(url::kDataScheme) && IsInMainFrame() &&

[Charlie Reis, 2017/02/15 23:36:43]

Why is this done from the NavigationHandleImpl destructor?  The test failures
seem to indicate that it's not safe to call GetRenderFrameHost() from there.

Maybe it would be better to do this somewhere related to the navigation commit
instead, like DidCommitNavigation?

[meacer, 2017/02/16 01:58:42]

Done, moved to DidCommitNavigation.

+      IsRendererInitiated()) {
+    GetRenderFrameHost()->AddMessageToConsole(
+        CONSOLE_MESSAGE_LEVEL_WARNING,
+        "Upcoming versions will block content-initiated top frame navigations "
+        "to data: URLs. For more information, see https://crbug.com/594215.");

[Charlie Reis, 2017/02/15 23:36:43]

This bug link doesn't seem like great documentation for people to reference. 
There's not much discussion of the reasoning or alternatives there, and it has a
link to a Google internal design doc (http://go/crbug-pseudo-urls).  Is there a
better link we can provide to developers?  Or maybe update the description of
that bug to provide a better overview?

[meacer, 2017/02/16 01:58:42]

Do you think blink intent to deprecate thread would be more useful? I can add a
goo.gl version of
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/GbVcuwg_QjM

I think it has the most complete context about this, and also has links to
tracking bugs and the feature dashboard.

[Charlie Reis, 2017/02/16 17:59:50]

Yes, a link to that intent would be perfect.  Thanks!

+  }
+
   if (!IsRendererDebugURL(url_))
     GetDelegate()->DidFinishNavigation(this);