Converted LayerImpl::bounds() to return SizeF.

cc/debug/debug_rect_history.cc

Index: cc/debug/debug_rect_history.cc
diff --git a/cc/debug/debug_rect_history.cc b/cc/debug/debug_rect_history.cc
index e8792e7789e884451ffc7800d38741813fbf7021..71611a64a45a99329920b7ce3fb85856e8e59051 100644
--- a/cc/debug/debug_rect_history.cc
+++ b/cc/debug/debug_rect_history.cc
@@ -78,9 +78,9 @@ void DebugRectHistory::SavePaintRects(LayerImpl* layer) {
 
   if (!layer->update_rect().IsEmpty() && layer->DrawsContent()) {
     float width_scale = layer->content_bounds().width() /
-                        static_cast<float>(layer->bounds().width());
+                        layer->bounds().width();
     float height_scale = layer->content_bounds().height() /
-                         static_cast<float>(layer->bounds().height());
+                         layer->bounds().height();
     gfx::Rect update_content_rect = gfx::ScaleToEnclosingRect(
         gfx::ToEnclosingRect(layer->update_rect()), width_scale, height_scale);
     debug_rects_.push_back(