VrShell: Exit fullscreen on app button press.

chrome/browser/android/vr_shell/vr_shell.cc

Index: chrome/browser/android/vr_shell/vr_shell.cc
diff --git a/chrome/browser/android/vr_shell/vr_shell.cc b/chrome/browser/android/vr_shell/vr_shell.cc
index e6b7c03fa09fffb402dac93a61041dfbb51a6428..37ed0ccaec4137e5176f744a529956425dc16d8c 100644
--- a/chrome/browser/android/vr_shell/vr_shell.cc
+++ b/chrome/browser/android/vr_shell/vr_shell.cc
@@ -488,6 +488,12 @@ void VrShell::ExitPresent() {
   delegate_provider_->ExitWebVRPresent();
 }
 
+void VrShell::ExitFullscreen() {
+  if (web_contents_ && web_contents_->IsFullscreen()) {
+    web_contents_->ExitFullscreen(false);
+  }
+}
+
 void VrShell::OnVRVsyncProviderRequest(
     device::mojom::VRVSyncProviderRequest request) {
   PostToGlThreadWhenReady(base::Bind(&VrShellGl::OnRequest,