Fix high-DPI on Windows to make use of DIP scaling in WebKit.

ui/surface/accelerated_surface_win.cc

Index: ui/surface/accelerated_surface_win.cc
diff --git a/ui/surface/accelerated_surface_win.cc b/ui/surface/accelerated_surface_win.cc
index 6b4e1b1965e13ec3cec574b5c71db97d3abb4eb0..e564271562e2c56fc284a555fc366bf1a4b4496e 100644
--- a/ui/surface/accelerated_surface_win.cc
+++ b/ui/surface/accelerated_surface_win.cc
@@ -26,6 +26,7 @@
 #include "base/time.h"
 #include "base/tracked_objects.h"
 #include "base/win/wrapped_window_proc.h"
+#include "ui/base/win/dpi.h"
 #include "ui/base/win/hwnd_util.h"
 #include "ui/gfx/rect.h"
 #include "ui/gl/gl_switches.h"
@@ -503,7 +504,19 @@ void AcceleratedPresenter::DoPresentAndAcknowledge(
   // If the window is a different size than the swap chain that is being
   // presented then drop the frame.
   gfx::Size window_size = GetWindowSize();
-  if (hidden_ && size != window_size) {
+#if defined(ENABLE_HIDPI)
+  // Check if the size mismatch is within allowable round off or truncation
+  // error.
+  gfx::Size dip_size = ui::win::ScreenToDIPSize(window_size);
+  gfx::Size pixel_size = ui::win::DIPToScreenSize(dip_size);
+  bool size_mismatch = abs(window_size.width() - size.width()) >
+      abs(window_size.width() - pixel_size.width()) ||
+      abs(window_size.height() - size.height()) >
+      abs(window_size.height() - pixel_size.height());
+#else
+  bool size_mismatch = size != window_size;
+#endif
+  if (hidden_ && size_mismatch) {
     TRACE_EVENT2("gpu", "EarlyOut_WrongWindowSize",
                  "backwidth", size.width(), "backheight", size.height());
     TRACE_EVENT2("gpu", "EarlyOut_WrongWindowSize2",
@@ -688,7 +701,6 @@ void AcceleratedPresenter::DoReleaseSurface() {
 
 void AcceleratedPresenter::PresentWithGDI(HDC dc) {
   TRACE_EVENT0("gpu", "PresentWithGDI");
-

[pkotwicz, 2013/01/23 19:39:23]

Nit: Keep the extra line

[kevers, 2013/01/23 21:37:00]

Done.

   if (!present_thread_->device())
     return;