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

content/app/content_main_runner.cc

Index: content/app/content_main_runner.cc
diff --git a/content/app/content_main_runner.cc b/content/app/content_main_runner.cc
index 24a528929e5acd2c7bfaa4ade8cca1bc32ebb621..04cfca28e3953dedf4338f91d275a29b866669c4 100644
--- a/content/app/content_main_runner.cc
+++ b/content/app/content_main_runner.cc
@@ -74,6 +74,8 @@
 #include <atlapp.h>
 #include <malloc.h>
 #include <cstring>
+#include "base/strings/string_number_conversions.h"

[sky, 2014/06/03 15:59:06]

nit: newline between 76/77.

[ananta, 2014/06/03 19:18:13]

Done.

+#include "ui/gfx/win/dpi.h"
 #elif defined(OS_MACOSX)
 #include "base/mac/scoped_nsautorelease_pool.h"
 #if !defined(OS_IOS)
@@ -658,6 +660,13 @@ class ContentMainRunnerImpl : public ContentMainRunner {
     if (command_line.HasSwitch(switches::kEnableHighResolutionTime))
       base::TimeTicks::SetNowIsHighResNowIfSupported();
 
+    if (command_line.HasSwitch(switches::kUseDeviceScaleFactor)) {
+      std::string scale_factor_string = command_line.GetSwitchValueASCII(
+          switches::kUseDeviceScaleFactor);
+      double scale_factor = 0;
+      if (base::StringToDouble(scale_factor_string, &scale_factor))
+        gfx::InitDeviceScaleFactor(scale_factor);
+    }

[sky, 2014/06/03 15:59:06]

Can you keep the DCHECK in GetDeviceScaleFactor() and have a call to
InitDeviceScaleFactor() here if no explicit scale factor?

[ananta, 2014/06/03 19:18:37]

Done.

     SetupCRT(command_line);
 #endif