Added Client-Hints.

chrome/browser/net/client_hints.cc

+// Copyright (c) 2012 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 "chrome/browser/net/client_hints.h"
+
+#include "base/bind.h"
+#include "base/stringprintf.h"
+#include "content/public/browser/browser_thread.h"
+#include "ui/gfx/screen.h"
+
+namespace {
+
+void FetchScreenInfoOnUIThread(ClientHints::ScreenInfo* info) {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  gfx::Display display = gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
+  info->width = display.GetSizeInPixel().width();
+  info->height = display.GetSizeInPixel().height();
+  info->pixel_ratio = display.device_scale_factor();
+}
+
+}  // namespace
+
+ClientHints::ClientHints() :
+    weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+}
+
+ClientHints::~ClientHints() {
+}
+
+bool ClientHints::RetrieveScreenInfo() {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
+  ClientHints::ScreenInfo* info = new ClientHints::ScreenInfo();
+  return content::BrowserThread::PostTaskAndReply(
+      content::BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&FetchScreenInfoOnUIThread, info),
+      base::Bind(&ClientHints::UpdateScreenInfo, weak_ptr_factory_.GetWeakPtr(),
+                 base::Owned(info)));

[mmenke, 2013/02/27 21:06:05]

What if the user changes screen resolution?

[bengr, 2013/03/06 00:34:19]

I presume that screen resolution changes are much rarer events than Chrome
restarts. In fact on iOS and Android devices, afaik, screen resolution can't be
changed. I therefore didn't see the point in the added code complexity to
support screen resolution changes mid browsing session.

On 2013/02/27 21:06:05, mmenke wrote:

[Ryan Sleevi, 2013/03/06 00:38:19]

Why isn't an orientation change considered a resolution change? I would expect
it to be

+}
+
+std::string ClientHints::GetScreenInfoHints() {

[mmenke, 2013/02/27 21:06:05]

optional:  Could just make this return a const string&.  Admittedly, one string
copy per request isn't going to matter, but seems completely unnecessary.

[bengr, 2013/03/06 00:34:19]

Done.

+  return screen_hints_;
+}
+
+void ClientHints::UpdateScreenInfo(ClientHints::ScreenInfo* info) {
+  if (info->height > 0 && info->width > 0 && info->pixel_ratio > 0.0) {
+    screen_hints_ = base::StringPrintf(
+        "dh=%d, dw=%d, dpr=%0.3g",
+        info->height, info->width, info->pixel_ratio);
+  }
+}
+