Switch app_shell default window size to 1280x720

This works better with our demo app and uses the aspect ratio of some HD monitors we're hoping to use.

BUG=none
TBR=oshima@chromium.org

Review URL: https://codereview.chromium.org/339963003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278459 0039d316-1c4b-4281-b951-d872f2087c98

apps/shell/browser/shell_desktop_controller.cc

@@ -232,7 +232,7 @@ void ShellDesktopController::CreateRootWindow() {
   // Set up basic pieces of ui::wm.
   gfx::Size size = GetPrimaryDisplaySize();
   if (size.IsEmpty())
-    size = gfx::Size(1366, 768);
+    size = gfx::Size(1280, 720);
 
   host_.reset(aura::WindowTreeHost::Create(gfx::Rect(size)));
   host_->InitHost();