Fix crash when backgrounding MojoShell on Android. Fixes issue #186.

services/native_viewport/onscreen_context_provider.cc

Index: services/native_viewport/onscreen_context_provider.cc
diff --git a/services/native_viewport/onscreen_context_provider.cc b/services/native_viewport/onscreen_context_provider.cc
index a7ba14b3d9c8dcf78a1463901cef86f799485ad6..90a98dc8106c6d02409526d842eb9e2b2a50aecb 100644
--- a/services/native_viewport/onscreen_context_provider.cc
+++ b/services/native_viewport/onscreen_context_provider.cc
@@ -32,8 +32,9 @@ void OnscreenContextProvider::SetAcceleratedWidget(
   widget_ = widget;
 
   if (widget_ == gfx::kNullAcceleratedWidget) {
-    if (command_buffer_impl_)
+    if (command_buffer_impl_) {
       command_buffer_impl_->DidLoseContext();
+    }
     return;
   }