Initialize device scale factor correctly on Android

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index cb8b30d22e3440891f9686ed2b622d5380feda98..405bb008c9e5f87ffa33667782047ffe7121e601 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -50,6 +50,10 @@
 #include "third_party/skia/include/core/SkPixelRef.h"
 #endif  // defined(OS_POSIX)
 
+#if defined(OS_ANDROID)
+#include "content/common/android/device_info.h"
+#endif  // defined(OS_ANDROID)
+
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebWidget.h"
 
 using WebKit::WebCompositionUnderline;
@@ -125,6 +129,9 @@ RenderWidget::RenderWidget(WebKit::WebPopupType popup_type,
       switches::kForceDeviceScaleFactor))
     device_scale_factor_ = static_cast<int>(device_scale_factor_);
   device_scale_factor_ = std::max(1.0f, device_scale_factor_);
+#elif defined(OS_ANDROID)
+  scoped_ptr<DeviceInfo> device_info(new DeviceInfo());
+  device_scale_factor_ = device_info->GetDPIScale();

[johnme, 2012/10/30 14:38:23]

There's also device scale factor logic in ui/gfx/display.cc, where
device_scale_factor_ is initialized using kForcedDeviceScaleFactor (which will
be wrong on Android).

Would it be better to move both this and the CrOS logic above into display.cc,
and make render_widget depend on that?

[Sami, 2012/10/31 11:12:57]

Good idea. I looked into this a little more and it doesn't seem very
straightforward to move this logic there. The problem is that
Display::device_scale_factor() is either 1 or the value from the command line --
i.e., it's not based on the real DPI on any of the ports as far as I can tell. I
don't want to go and change it to match the real DPI because I don't have a good
way of testing this on platforms other than Android.

On the plus side, it turns out that we can just add OS_ANDROID to the list on
line 124 and things will work.

I've added a TODO to clean this up.

 #endif
 }