Scale to DIPs in ppb_graphics2d_impl for proper invalidation

ui/gfx/rect.cc

Index: ui/gfx/rect.cc
diff --git a/ui/gfx/rect.cc b/ui/gfx/rect.cc
index 300b8adbf0f746d9caf6643e9c3032751a1232e3..9a254d41882d1545fde9145f9aee90702729bb94 100644
--- a/ui/gfx/rect.cc
+++ b/ui/gfx/rect.cc
@@ -4,6 +4,8 @@
 
 #include "ui/gfx/rect.h"
 
+#include <math.h>
+
 #if defined(OS_WIN)
 #include <windows.h>
 #elif defined(OS_MACOSX)
@@ -44,6 +46,14 @@ Rect::Rect(const gfx::Point& origin, const gfx::Size& size)
 
 Rect::~Rect() {}
 
+void Rect::ScaleBounds(float scale) {
+  int left = static_cast<int>(floorf(x() * scale));
+  int top = static_cast<int>(floorf(y() * scale));
+  int right = static_cast<int>(ceilf((x() + width()) * scale));
+  int bottom = static_cast<int>(ceilf((y() + height()) * scale));
+  SetRect(left, top, right - left, bottom - top);
+}
+
 #if defined(OS_WIN)
 Rect::Rect(const RECT& r)
     : RectBaseT(gfx::Point(r.left, r.top)) {