Do not convert from RectF to Rect by flooring.

content/browser/renderer_host/backing_store_mac.mm

Index: content/browser/renderer_host/backing_store_mac.mm
diff --git a/content/browser/renderer_host/backing_store_mac.mm b/content/browser/renderer_host/backing_store_mac.mm
index 592e85c30adefc29cb13b084260521d849f527c2..9bb8b6d56ffa616723f2da36be86048b6fe03b57 100644
--- a/content/browser/renderer_host/backing_store_mac.mm
+++ b/content/browser/renderer_host/backing_store_mac.mm
@@ -16,6 +16,7 @@
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "ui/gfx/rect.h"
+#include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/scoped_cg_context_save_gstate_mac.h"
 #include "ui/surface/transport_dib.h"
 
@@ -85,7 +86,8 @@ void BackingStoreMac::PaintToBackingStore(
     return;
 
   gfx::Size pixel_size = size().Scale(device_scale_factor_);
-  gfx::Rect pixel_bitmap_rect = bitmap_rect.Scale(scale_factor);
+  gfx::Rect pixel_bitmap_rect =
+      gfx::ToEnclosingRect(bitmap_rect.Scale(scale_factor));
 
   size_t bitmap_byte_count =
       pixel_bitmap_rect.width() * pixel_bitmap_rect.height() * 4;
@@ -104,7 +106,8 @@ void BackingStoreMac::PaintToBackingStore(
 
   for (size_t i = 0; i < copy_rects.size(); i++) {
     const gfx::Rect& copy_rect = copy_rects[i];
-    gfx::Rect pixel_copy_rect = copy_rect.Scale(scale_factor);
+    gfx::Rect pixel_copy_rect =
+        gfx::ToEnclosingRect(copy_rect.Scale(scale_factor));
 
     // Only the subpixels given by copy_rect have pixels to copy.
     base::mac::ScopedCFTypeRef<CGImageRef> image(