Fix crash if VR opened with too many tabs.

If you have too many open, we'd crash from exhausing all JNI references.
Shouldn't be an issue in practice but saw it from 726426
BUG=726426

Change-Id: I30ac884275154068a0232b62dae7b22e00d9e5e3
Reviewed-on: https://chromium-review.googlesource.com/893532Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Commit-Queue: Yaron Friedman <yfriedman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533010}

chrome/browser/android/vr_shell/vr_shell.cc

@@ -71,6 +71,7 @@
 #include "url/gurl.h"
 
 using base::android::JavaParamRef;
+using base::android::ScopedJavaLocalRef;
 
 namespace vr_shell {
 
@@ -457,9 +458,8 @@ void VrShell::OnTabListCreated(JNIEnv* env,
 void VrShell::ProcessTabArray(JNIEnv* env, jobjectArray tabs, bool incognito) {
   size_t len = env->GetArrayLength(tabs);
   for (size_t i = 0; i < len; ++i) {
-    jobject jtab = env->GetObjectArrayElement(tabs, i);
-    TabAndroid* tab =
-        TabAndroid::GetNativeTab(env, JavaParamRef<jobject>(env, jtab));
+    ScopedJavaLocalRef<jobject> j_tab(env, env->GetObjectArrayElement(tabs, i));
+    TabAndroid* tab = TabAndroid::GetNativeTab(env, j_tab);
     ui_->AppendToTabList(incognito, tab->GetAndroidId(), tab->GetTitle());
   }
 }