cc: Only allow trees created at the current viewport size to draw.

cc/layer_tree_host_impl.cc

Index: cc/layer_tree_host_impl.cc
diff --git a/cc/layer_tree_host_impl.cc b/cc/layer_tree_host_impl.cc
index 607a50c2344ce9bc1810702f5238d2507b535de4..23e826333d959a58cd1b95e925c16c568bb3f9bf 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -223,6 +223,10 @@ bool LayerTreeHostImpl::canDraw()
         TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw empty viewport");
         return false;
     }
+    if (deviceViewportSize() != activeTree()->device_viewport_size()) {
+        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw viewport resize incomplete");
+        return false;
+    }
     if (!m_renderer) {
         TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw no renderer");
         return false;
@@ -1095,6 +1099,11 @@ void LayerTreeHostImpl::setViewportSize(const gfx::Size& layoutViewportSize, con
     m_layoutViewportSize = layoutViewportSize;
     m_deviceViewportSize = deviceViewportSize;

[danakj, 2013/02/13 05:44:30]

Can you just remove the m_deviceViewportSize from the host then? It's just
duplicating the value on the pending tree now, no?

In fact can you move both viewport sizes to the trees? Seems like this whole
function is redundant with what happens in the LTImpl.

 
+    if (m_settings.implSidePainting)
+        pendingTree()->SetDeviceViewportSize(deviceViewportSize);
+    else
+        activeTree()->SetDeviceViewportSize(deviceViewportSize);
+
     updateMaxScrollOffset();
 
     if (m_renderer)