Pass the device scale factor in the command line to renderer processes.

content/public/common/content_switches.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 "content/public/common/content_switches.h"
 
 #include "base/command_line.h"
 
 namespace switches {
 
@@ skipping 392 matching lines @@
 
 // When using CPU rasterizing generate low resolution tiling. Low res
 // tiles may be displayed during fast scrolls especially on slower devices.
 const char kEnableLowResTiling[] = "enable-low-res-tiling";
 
 // See comment for kEnableCompositingForFixedPosition.
 const char kEnableHighDpiCompositingForFixedPosition[] =
      "enable-high-dpi-fixed-position-compositing";
 
 #if defined(OS_WIN)
+// Device scale factor passed to certain processes like renderers, etc.
+const char kDeviceScaleFactor[]     = "device-scale-factor";
+
 // Disable the Legacy Window which corresponds to the size of the WebContents.
 const char kDisableLegacyIntermediateWindow[] = "disable-legacy-window";
 
 // Enables the DirectWrite font rendering system on windows.
 const char kEnableDirectWrite[]             = "enable-direct-write";
 
 // Use high resolution timers for TimeTicks.
 const char kEnableHighResolutionTime[]      = "enable-high-resolution-time";
 
 // Enable the Win32K process mitigation policy for renderer processes which
@@ skipping 555 matching lines @@
 
 // Disables support for Core Animation plugins. This is triggered when
 // accelerated compositing is disabled. See http://crbug.com/122430 .
 const char kDisableCoreAnimationPlugins[] =
     "disable-core-animation-plugins";
 #endif
 
 // Don't dump stuff here, follow the same order as the header.
 
 }  // namespace switches