mac: ensure ui::Compositor exists for visible RWHVs

content/browser/renderer_host/render_widget_host_view_mac.mm

Index: content/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 86481a97da9b4ab23e3ceb789bcc0e2c0b0063de..cda7d0196d15562d80c6a41af0ac8686b4ce4bca 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -594,6 +594,9 @@ RenderWidgetHostViewMac::RenderWidgetHostViewMac(RenderWidgetHost* widget,
         ->GetInputEventRouter()
         ->AddSurfaceIdNamespaceOwner(GetSurfaceIdNamespace(), this);
   }
+
+  if (!render_widget_host_->is_hidden())
+    EnsureBrowserCompositorView();
 }
 
 RenderWidgetHostViewMac::~RenderWidgetHostViewMac() {
@@ -1477,8 +1480,7 @@ void RenderWidgetHostViewMac::OnSwapCompositorFrame(
     gfx::Size dip_size = gfx::ConvertSizeToDIP(scale_factor, pixel_size);
 
     root_layer_->SetBounds(gfx::Rect(dip_size));
-    if (!render_widget_host_->is_hidden()) {
-      EnsureBrowserCompositorView();
+    if (!browser_compositor->compositor()) {

[danakj, 2016/05/24 00:34:40]

Is this inverted?

if (!a)
  a->Foo()

is a crash

[ccameron, 2016/05/24 00:37:39]

Just needs "if (browser_compositor)"

       browser_compositor_->compositor()->SetScaleAndSize(
           scale_factor, pixel_size);
     }