Fix touch scaling for high dpi windows.

ui/base/win/dpi.cc

Index: ui/base/win/dpi.cc
diff --git a/ui/base/win/dpi.cc b/ui/base/win/dpi.cc
index b618df91715c9b9105b9f8c064647673c96011cc..cc713319882f67ccd6620d6b647866af5e68c80c 100644
--- a/ui/base/win/dpi.cc
+++ b/ui/base/win/dpi.cc
@@ -8,6 +8,7 @@
 
 #include "base/win/scoped_hdc.h"
 #include "ui/base/layout.h"
+#include "base/win/registry.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/point_conversions.h"
 #include "ui/gfx/rect_conversions.h"
@@ -30,6 +31,24 @@ float GetDeviceScaleFactorImpl() {
 #endif
 }
 
+FARPROC GetProcAddressWrapper(LPCSTR module_name, LPCSTR proc_name) {
+  HMODULE module = ::GetModuleHandleA(module_name);
+  if (module) {
+    return ::GetProcAddress(module, proc_name);
+  }
+  return NULL;
+}
+
+BOOL IsProcessDPIAwareWrapper() {
+  typedef BOOL(WINAPI *IsProcessDPIAwarePtr)(VOID);
+  IsProcessDPIAwarePtr is_process_dpi_aware_func =
+      reinterpret_cast<IsProcessDPIAwarePtr>(
+          GetProcAddressWrapper("user32.dll", "IsProcessDPIAware"));
+  if (is_process_dpi_aware_func)
+    return is_process_dpi_aware_func();
+  return FALSE;
+}
+
 }  // namespace
 
 namespace ui {
@@ -65,7 +84,7 @@ void EnableHighDPISupport() {
   typedef BOOL(WINAPI *SetProcessDPIAwarePtr)(VOID);
   SetProcessDPIAwarePtr set_process_dpi_aware_func =
       reinterpret_cast<SetProcessDPIAwarePtr>(
-          GetProcAddress(GetModuleHandleA("user32.dll"), "SetProcessDPIAware"));
+          GetProcAddressWrapper("user32.dll", "SetProcessDPIAware"));
   if (set_process_dpi_aware_func)
     set_process_dpi_aware_func();
 }
@@ -103,6 +122,33 @@ gfx::Size DIPToScreenSize(const gfx::Size& dip_size) {
   return gfx::ToFlooredSize(gfx::ScaleSize(dip_size, GetDeviceScaleFactor()));
 }
 
+double GetDPIScaleFromRegistry() {
+  static double scale = -1.0;
+  if (scale == -1.0) {
+    double result = 1.0;
+    if (!IsProcessDPIAwareWrapper()) {
+      //HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics\AppliedDPI

[Ryan Sleevi, 2013/03/05 18:32:56]

nit: space between //

+      base::win::RegKey key(HKEY_CURRENT_USER,
+                            L"Control Panel\\Desktop\\WindowMetrics",
+                            KEY_QUERY_VALUE);
+
+      if (key.Valid()) {
+        DWORD value = 0;
+        if (key.ReadValueDW(L"AppliedDPI", &value) == ERROR_SUCCESS) {
+          result = ((double)value) / kDefaultDPIX;

[Ryan Sleevi, 2013/03/05 18:32:56]

style: Don't do C-casts

+        }
+      }
+    }
+    scale = result;
+  }
+
+  // Safety test to ignore invalid settings.
+  if (scale <= 0.0)
+    scale = 1.0;
+
+  return scale;
+}
+
 }  // namespace win
 
 }  // namespace ui