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

content/app/content_main_runner.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/app/content_main_runner.h"
 
 #include <stdlib.h>
 
 #include "base/allocator/allocator_extension.h"
 #include "base/at_exit.h"
@@ skipping 31 matching lines @@
 #include "content/public/common/sandbox_init.h"
 #include "content/renderer/in_process_renderer_thread.h"
 #include "content/utility/in_process_utility_thread.h"
 #include "crypto/nss_util.h"
 #include "ipc/ipc_descriptors.h"
 #include "ipc/ipc_switches.h"
 #include "media/base/media.h"
 #include "sandbox/win/src/sandbox_types.h"
 #include "ui/base/ui_base_paths.h"
 #include "ui/base/ui_base_switches.h"
-#include "ui/gfx/win/dpi.h"
 
 #if defined(USE_TCMALLOC)
 #include "third_party/tcmalloc/chromium/src/gperftools/malloc_extension.h"
 #if defined(TYPE_PROFILING)
 #include "base/allocator/type_profiler.h"
 #include "base/allocator/type_profiler_tcmalloc.h"
 #endif
 #endif
 
 #if !defined(OS_IOS)
 #include "content/app/mojo/mojo_init.h"
 #include "content/browser/gpu/gpu_process_host.h"
 #include "content/browser/renderer_host/render_process_host_impl.h"
 #include "content/browser/utility_process_host_impl.h"
 #include "content/public/plugin/content_plugin_client.h"
 #include "content/public/renderer/content_renderer_client.h"
 #include "content/public/utility/content_utility_client.h"
 #endif
 
 #if defined(OS_WIN)
 #include <atlbase.h>
 #include <atlapp.h>
 #include <malloc.h>
 #include <cstring>
+
+#include "base/strings/string_number_conversions.h"
+#include "ui/base/win/dpi_setup.h"
+#include "ui/gfx/win/dpi.h"
 #elif defined(OS_MACOSX)
 #include "base/mac/scoped_nsautorelease_pool.h"
 #if !defined(OS_IOS)
 #include "base/power_monitor/power_monitor_device_source.h"
 #include "content/browser/mach_broker_mac.h"
 #include "content/common/sandbox_init_mac.h"
 #endif  // !OS_IOS
 #endif  // OS_WIN
 
 #if defined(OS_POSIX)
@@ skipping 563 matching lines @@
       base::PowerMonitorDeviceSource::AllocateSystemIOPorts();
     }
 
     if (!process_type.empty() &&
         (!delegate_ || delegate_->ShouldSendMachPort(process_type))) {
       MachBroker::ChildSendTaskPortToParent();
     }
 #elif defined(OS_WIN)
     if (command_line.HasSwitch(switches::kEnableHighResolutionTime))
       base::TimeTicks::SetNowIsHighResNowIfSupported();
+    
+    bool init_device_scale_factor = true;

[jam, 2014/06/04 00:29:14]

this command line flag is only passed to the renderer, so the code to respond
should only be called in content/renderer. Can you put this in RendererMain, or
did you put this early because there's something between this line and that
which requires this?

+    if (command_line.HasSwitch(switches::kDeviceScaleFactor)) {
+      std::string scale_factor_string = command_line.GetSwitchValueASCII(
+          switches::kDeviceScaleFactor);
+      double scale_factor = 0;
+      if (base::StringToDouble(scale_factor_string, &scale_factor)) {
+        init_device_scale_factor = false;
+        gfx::InitDeviceScaleFactor(scale_factor);
+      }
+    }
+    if (init_device_scale_factor)
+      ui::win::InitDeviceScaleFactor();
 
     SetupCRT(command_line);
 #endif
 
 #if defined(OS_POSIX)
     if (!process_type.empty()) {
       // When you hit Ctrl-C in a terminal running the browser
       // process, a SIGINT is delivered to the entire process group.
       // When debugging the browser process via gdb, gdb catches the
       // SIGINT for the browser process (and dumps you back to the gdb
@@ skipping 130 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(ContentMainRunnerImpl);
 };
 
 // static
 ContentMainRunner* ContentMainRunner::Create() {
   return new ContentMainRunnerImpl();
 }
 
 }  // namespace content