Implementation of device metrics emulation in render view.

cc/layers/heads_up_display_layer.cc

Index: cc/layers/heads_up_display_layer.cc
===================================================================
--- cc/layers/heads_up_display_layer.cc	(revision 221161)
+++ cc/layers/heads_up_display_layer.cc	(working copy)
@@ -9,6 +9,7 @@
 #include "base/debug/trace_event.h"
 #include "cc/layers/heads_up_display_layer_impl.h"
 #include "cc/trees/layer_tree_host.h"
+#include "ui/gfx/size_conversions.h"
 
 namespace cc {
 
@@ -26,6 +27,16 @@
       device_viewport.width() / device_scale_factor,
       device_viewport.height() / device_scale_factor);
 
+  if (parent()) {
+    // The root layer may have the transform set. As we still want to be shown

[aelias_OOO_until_Jul13, 2013/09/13 23:51:44]

This should be addressed on the Blink side instead.  You can set a inverse
transform on the HUD layer there or change where the transform is applied so
that the HUD layer isn't under it.

[dgozman, 2013/09/19 10:17:11]

AFAIK, blink doesn't know about the HUD layer. Ideally, we should place HUD
layer as a sibling to blink root layer. Not sure if that's the right choice
though. WDYT?

+    // at the corner of visible viewport, apply inverted transform to it.
+    gfx::Transform invert;
+    gfx::RectF rect(device_viewport_in_layout_pixels);
+    if (parent()->transform().TransformRectReverse(&rect)) {
+      device_viewport_in_layout_pixels = gfx::ToFlooredSize(rect.size());
+    }
+  }
+
   gfx::Size bounds;
   gfx::Transform matrix;
   matrix.MakeIdentity();