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

content/browser/renderer_host/render_process_host_impl.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.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 147 matching lines @@
 #include "content/browser/renderer_host/compositor_impl_android.h"
 #include "content/common/gpu/client/gpu_memory_buffer_impl_surface_texture.h"
 #endif
 
 #if defined(OS_MACOSX)
 #include "content/common/gpu/client/gpu_memory_buffer_impl_io_surface.h"
 #include "ui/gl/io_surface_support_mac.h"
 #endif
 
 #if defined(OS_WIN)
+#include "base/strings/string_number_conversions.h"
 #include "base/win/scoped_com_initializer.h"
 #include "content/common/font_cache_dispatcher_win.h"
 #include "content/common/sandbox_win.h"
+#include "ui/gfx/win/dpi.h"
 #endif
 
 #if defined(ENABLE_WEBRTC)
 #include "content/browser/media/webrtc_internals.h"
 #include "content/browser/renderer_host/media/media_stream_track_metrics_host.h"
 #include "content/browser/renderer_host/media/webrtc_identity_service_host.h"
 #include "content/common/media/media_stream_messages.h"
 #endif
 
 extern bool g_exited_main_message_loop;
@@ skipping 849 matching lines @@
     command_line->AppendSwitchASCII(switches::kForceFieldTrials,
                                     field_trial_states);
   }
 
   GetContentClient()->browser()->AppendExtraCommandLineSwitches(
       command_line, GetID());
 
   if (content::IsPinchToZoomEnabled())
     command_line->AppendSwitch(switches::kEnablePinch);
 
+#if defined(OS_WIN)
+  command_line->AppendSwitchASCII(switches::kDeviceScaleFactor,
+                                  base::DoubleToString(gfx::GetDPIScale()));
+#endif
+
   AppendCompositorCommandLineFlags(command_line);
 }
 
 void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     const CommandLine& browser_cmd,
     CommandLine* renderer_cmd) const {
   // Propagate the following switches to the renderer command line (along
   // with any associated values) if present in the browser command line.
   static const char* const kSwitchNames[] = {
     switches::kAllowInsecureWebSocketFromHttpsOrigin,
@@ skipping 1198 matching lines @@
 void RenderProcessHostImpl::GpuMemoryBufferAllocated(
     IPC::Message* reply,
     const gfx::GpuMemoryBufferHandle& handle) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   ChildProcessHostMsg_SyncAllocateGpuMemoryBuffer::WriteReplyParams(reply,
                                                                     handle);
   Send(reply);
 }
 
 }  // namespace content