Move navigation and frame tree classes to a new frame_host/ directory.

content/browser/frame_host/DEPS

Index: content/browser/frame_host/DEPS
diff --git a/content/browser/frame_host/DEPS b/content/browser/frame_host/DEPS
new file mode 100644
index 0000000000000000000000000000000000000000..85fb015231940618f769c2095a8535e2c6df4401
--- /dev/null
+++ b/content/browser/frame_host/DEPS
@@ -0,0 +1,22 @@
+include_rules = [
+  # The frame_host files should only call upwards in the layering via the
+  # delegate interfaces.
+  "-content/browser/web_contents",
+  "-content/public/browser/web_contents.h",
+  "-content/public/browser/web_contents_delegate.h",
+  "-content/public/browser/web_contents_view.h",
+]
+
+specific_include_rules = {
+  ".*_(unit|browser)test\.cc": [
+    "+content/browser/web_contents",
+    "+content/public/browser/web_contents_delegate.h",
+  ],
+  ".*interstitial_page_impl\.cc": [
+    # TODO(nasko): This should be removed once we remove
+    # WebContentsObserver as the method of telling interstitial pages to
+    # clean themselves up.
+    "+content/browser/web_contents",
+    "+content/public/browser/web_contents_delegate.h",
+  ],
+}