Scale to DIPs in ppb_graphics2d_impl for proper invalidation

webkit/plugins/ppapi/ppb_graphics_2d_impl.h

Index: webkit/plugins/ppapi/ppb_graphics_2d_impl.h
diff --git a/webkit/plugins/ppapi/ppb_graphics_2d_impl.h b/webkit/plugins/ppapi/ppb_graphics_2d_impl.h
index cec39c61e5e24785525c456a9a8fe03adfd980d7..277fc5cb6556be0d96d20bc768cf407107b09480 100644
--- a/webkit/plugins/ppapi/ppb_graphics_2d_impl.h
+++ b/webkit/plugins/ppapi/ppb_graphics_2d_impl.h
@@ -15,8 +15,10 @@
 #include "ppapi/shared_impl/tracked_callback.h"
 #include "ppapi/thunk/ppb_graphics_2d_api.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebCanvas.h"
+#include "webkit/plugins/webkit_plugins_export.h"
 
 namespace gfx {
+class Point;
 class Rect;
 }
 
@@ -75,6 +77,15 @@ class PPB_Graphics2D_Impl : public ::ppapi::Resource,
 
   PPB_ImageData_Impl* image_data() { return image_data_.get(); }
 
+  // Scale |op_rect| to logical pixels, taking care to include partially-
+  // covered logical pixels (aka DIPs). Also scale optional |delta| to logical
+  // pixels as well for scrolling cases. Returns false for scrolling cases where
+  // scaling either |op_rect| or |delta| would require scrolling to fall back to
+  // invalidation due to rounding errors, true otherwise.
+  WEBKIT_PLUGINS_EXPORT static bool ConvertToLogicalPixels(float scale,
+                                                           gfx::Rect* op_rect,
+                                                           gfx::Point* delta);
+
  private:
   explicit PPB_Graphics2D_Impl(PP_Instance instance);