[MD Settings] PROOF OF CONCEPT - DO NOT LAND - URL rewrite

components/sessions/content/content_serialized_navigation_driver.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/sessions/content/content_serialized_navigation_driver.h"
 
 #include "base/memory/singleton.h"
 #include "build/build_config.h"
 #include "components/sessions/core/serialized_navigation_entry.h"
 #include "content/public/common/page_state.h"
 #include "content/public/common/referrer.h"
 #include "content/public/common/url_constants.h"
 
+SESSIONS_EXPORT bool (*g_settingsFlagFunc)(void);
+
 namespace sessions {
 
 namespace {
 const int kObsoleteReferrerPolicyAlways = 0;
 const int kObsoleteReferrerPolicyDefault = 1;
 const int kObsoleteReferrerPolicyNever = 2;
 const int kObsoleteReferrerPolicyOrigin = 3;
 }  // namespace
 
 // static
@@ skipping 82 matching lines @@
   // No need to compare the policy, as it doesn't change during
   // sanitization. If there has been a change, the referrer needs to be
   // stripped from the page state as well.
   if (navigation->referrer_url_ != new_referrer.url) {
     navigation->referrer_url_ = GURL();
     navigation->referrer_policy_ = GetDefaultReferrerPolicy();
     navigation->encoded_page_state_ =
         StripReferrerFromPageState(navigation->encoded_page_state_);
   }
 
+  if (g_settingsFlagFunc &&

[Dan Beam, 2016/07/21 23:36:18]

can we plumb this through ContentBrowserClient?

class ContentBrowserClient {
  virtual GURL RewriteURLForSessionRestore(const GURL& url) const = 0;
};

GURL ChromeContentBrowserClient::RewriteURLForSessionRestore(
    const GURL& url) const {
  GURL reversed_url(url);
  HandleWebUIReverse(&reversed_url, nullptr);
  return reversed_url;
}

[groby-ooo-7-16, 2016/07/26 00:23:09]

That was the plan, until I started digging deeper...
Not quite as trivial, since we also need to add the uber host, depending on what
direction we're going. The function that does that is WillHandleBrowserAboutURL.
 

And if we wanted to do the "right" thing, we essentially need to do
BrowserURLHandlerImpl::RewriteURLIfNecessary, but restricted to the handlers we
care about (i.e. WebUI)

Which we could do without adding additional hooks:

    if (navigation->virtual_url_.SchemeIs(content::kChromeUIScheme)) {
        BrowserURLHandlerImpl::GetInstance()->RewriteURLIfNecessary(
            &navigation->original_request_url_, browser_context,
&reverse_on_redirect);
        navigation->encoded_page_state_ =
            content::PageState::CreateFromURL(navigation->original_request_url_)
                 .ToEncodedData();
    }

Except the missing |browser_context_| here. I'm not sure why we thought that
rewriting URLs based on profile is ever a good idea, but it doesn't look like
one from here. (I'm wildly speculating that extensions that register URL
overrides will also run into trouble if they change their overrides. As will NTP
changes. Oh well.)

Anyways, that means none of the above schemes will work, and things need to be
handcoded. Yay us.

We _could_ hack things so that WillHandleBrowserAboutURL can deal with nullptrs,
but we might as well just hardcode the URL handling as a separate callback at
this point.

So close, and yet so far.

+      navigation->virtual_url_.SchemeIs(content::kChromeUIScheme)) {
+    if (g_settingsFlagFunc() &&
+        navigation->original_request_url().spec() ==
+            "chrome://chrome/settings/") {
+      navigation->original_request_url_ = GURL("chrome://settings/");
+      navigation->encoded_page_state_ =
+          content::PageState::CreateFromURL(navigation->original_request_url_)
+              .ToEncodedData();
+    }
+    if (!g_settingsFlagFunc() &&
+        navigation->original_request_url().spec() == "chrome://settings/") {
+      navigation->original_request_url_ = GURL("chrome://chrome/settings/");
+      navigation->encoded_page_state_ =
+          content::PageState::CreateFromURL(navigation->original_request_url_)
+              .ToEncodedData();
+    }
+  }
+
 #if defined(OS_ANDROID)
   // Rewrite the old new tab and welcome page URLs to the new NTP URL.
   if (navigation->virtual_url_.SchemeIs(content::kChromeUIScheme) &&
       (navigation->virtual_url_.host() == "welcome" ||
        navigation->virtual_url_.host() == "newtab")) {
     navigation->virtual_url_ = GURL("chrome-native://newtab/");
     navigation->original_request_url_ = navigation->virtual_url_;
     navigation->encoded_page_state_ = content::PageState::CreateFromURL(
         navigation->virtual_url_).ToEncodedData();
   }
 #endif  // defined(OS_ANDROID)
 }
 
 std::string ContentSerializedNavigationDriver::StripReferrerFromPageState(
       const std::string& page_state) const {
   return content::PageState::CreateFromEncodedData(page_state)
       .RemoveReferrer()
       .ToEncodedData();
 }
 
 }  // namespace sessions