Scale to DIPs in ppb_graphics2d_impl for proper invalidation

ui/gfx/rect_unittest.cc

Index: ui/gfx/rect_unittest.cc
diff --git a/ui/gfx/rect_unittest.cc b/ui/gfx/rect_unittest.cc
index 4eefdd69f5622da8e6a058cfafd21e77eb37efd4..1328cae23095df7e6564706a020bad4aa0fee1c5 100644
--- a/ui/gfx/rect_unittest.cc
+++ b/ui/gfx/rect_unittest.cc
@@ -344,6 +344,45 @@ TEST(RectTest, SkRectToRect) {
   EXPECT_EQ(src, gfx::SkRectToRect(skrect));
 }
 
+TEST(RectTest, ScaleRect) {
+  static const struct {
+    int x1;  // rect 1
+    int y1;
+    int w1;
+    int h1;
+    int x2;  // rect 2
+    int y2;
+    int w2;
+    int h2;
+    float scale;
+  } tests[] = {
+    { 0, 0, 0, 0, 0, 0, 0, 0, 1.0 },
+    { 0, 0, 0, 0, 0, 0, 0, 0, 2.0 },
+    { 0, 0, 4, 4, 0, 0, 2, 2, 0.5 },
+    { 1, 1, 4, 4, 0, 0, 3, 3, 0.5 },
+    { 53, 75, 100, 100, 53, 75, 100, 100, 1.0 },
+    { 53, 75, 100, 100, 106, 150, 200, 200, 2.0 },
+    { 53, 75, 100, 100, 26, 37, 51, 51, 0.5 },
+    { 53, 74, 100, 100, 26, 37, 51, 50, 0.5 },
+    { -1, -1, 100, 100, -1, -1, 51, 51, 0.5 },
+    { -2, -2, 100, 100, -1, -1, 50, 50, 0.5 },
+    { -101, -100, 50, 50, -51, -50, 26, 25, 0.5 }
+  };
+  for (size_t i = 0; i < ARRAYSIZE_UNSAFE(tests); ++i) {
+    gfx::Rect r1(tests[i].x1, tests[i].y1, tests[i].w1, tests[i].h1);
+    gfx::Rect r2(tests[i].x2, tests[i].y2, tests[i].w2, tests[i].h2);
+    gfx::Rect orig(tests[i].x1, tests[i].y1, tests[i].w1, tests[i].h1);
+    r1.ScaleBounds(tests[i].scale);
+    EXPECT_TRUE(r1.Equals(r2));
+    r1.ScaleBounds(1.0 / tests[i].scale);
+    EXPECT_TRUE(r1.x() <= orig.x());
+    EXPECT_TRUE(r1.y() <= orig.y());
+    EXPECT_TRUE(r1.x() + r1.width() >= orig.x() + orig.width());
+    EXPECT_TRUE(r1.y() + r1.height() >= orig.y() + orig.height());
+  }
+
+}
+
 #if defined(OS_WIN)
 TEST(RectTest, ConstructAndAssign) {
   const RECT rect_1 = { 0, 0, 10, 10 };