Add HiDPI flag for Windows.

The flag is currently disabled by default.

BUG=243445

Review URL: https://chromiumcodereview.appspot.com/16196008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@204939 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 23 insertions, 8 deletions

diff --git a/ui/base/ui_base_switches.cc b/ui/base/ui_base_switches.cc
index f4c3b7c..51a9546 100644
--- a/ui/base/ui_base_switches.cc
+++ b/ui/base/ui_base_switches.cc
@@ -39,6 +39,9 @@ const char kEnableTouchEditing[] = "enable-touch-editing";
 // Enables the Views textfield on Windows.
 const char kEnableViewsTextfield[] = "enable-views-textfield";
 
+// Enables/Disables High DPI support (windows)
+const char kHighDPISupport[] = "high-dpi-support";
+
 // Overrides the device scale factor for the browser UI and the contents.
 const char kForceDeviceScaleFactor[] = "force-device-scale-factor";
 
diff --git a/ui/base/ui_base_switches.h b/ui/base/ui_base_switches.h
index da5fd4b..dfaed583 100644
--- a/ui/base/ui_base_switches.h
+++ b/ui/base/ui_base_switches.h
@@ -24,6 +24,7 @@ UI_EXPORT extern const char kEnableTouchDragDrop[];
 UI_EXPORT extern const char kEnableTouchEditing[];
 UI_EXPORT extern const char kEnableViewsTextfield[];
 UI_EXPORT extern const char kForceDeviceScaleFactor[];
+UI_EXPORT extern const char kHighDPISupport[];
 UI_EXPORT extern const char kHighlightMissingScaledResources[];
 UI_EXPORT extern const char kLang[];
 UI_EXPORT extern const char kLocalePak[];
diff --git a/ui/base/win/dpi.cc b/ui/base/win/dpi.cc
index 75d63bb..9b2db5b 100644
--- a/ui/base/win/dpi.cc
+++ b/ui/base/win/dpi.cc
@@ -5,10 +5,11 @@
 #include "ui/base/win/dpi.h"
 
 #include <windows.h>
-
+#include "base/command_line.h"
 #include "base/win/scoped_hdc.h"
 #include "ui/base/layout.h"
 #include "base/win/registry.h"
+#include "ui/base/ui_base_switches.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/point_conversions.h"
 #include "ui/gfx/rect_conversions.h"
@@ -19,16 +20,26 @@ namespace {
 int kDefaultDPIX = 96;
 int kDefaultDPIY = 96;
 
+bool IsHighDPIEnabled() {
+  // Default is disabled.
+  if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kHighDPISupport)) {
+    return CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+        switches::kHighDPISupport).compare("1") == 0;
+  }
+  return false;
+}
+
 float GetDeviceScaleFactorImpl() {
 #if defined(ENABLE_HIDPI)
-  float scale = gfx::Display::HasForceDeviceScaleFactor() ?
-      gfx::Display::GetForcedDeviceScaleFactor() : ui::GetDPIScale();
-  // Quantize to nearest supported scale factor.
-  scale = ui::GetScaleFactorScale(ui::GetScaleFactorFromScale(scale));
-  return scale;
-#else
-  return 1.0f;
+  if (IsHighDPIEnabled()) {
+    float scale = gfx::Display::HasForceDeviceScaleFactor() ?
+        gfx::Display::GetForcedDeviceScaleFactor() : ui::GetDPIScale();
+    // Quantize to nearest supported scale factor.
+    scale = ui::GetScaleFactorScale(ui::GetScaleFactorFromScale(scale));
+    return scale;
+  }
 #endif
+  return 1.0f;
 }
 
 BOOL IsProcessDPIAwareWrapper() {