Update the comment for checking null in needtouchevents.

Add the header in WebCoreJni.cpp so that LOGE will be print out.
diff --git a/WebKit/android/jni/WebCoreJni.cpp b/WebKit/android/jni/WebCoreJni.cpp
index b757e3a..e7088b2 100644
--- a/WebKit/android/jni/WebCoreJni.cpp
+++ b/WebKit/android/jni/WebCoreJni.cpp
@@ -26,6 +26,7 @@
 
 #include "config.h"
 
+#include "NotImplemented.h"
 #include "WebCoreJni.h"
 #include "jni_utility.h"
 #include <jni.h>
diff --git a/WebKit/android/jni/WebViewCore.cpp b/WebKit/android/jni/WebViewCore.cpp
index 1cf96d5..359da03 100644
--- a/WebKit/android/jni/WebViewCore.cpp
+++ b/WebKit/android/jni/WebViewCore.cpp
@@ -904,8 +904,8 @@
 #if ENABLE(TOUCH_EVENTS) // Android
     JNIEnv* env = JSC::Bindings::getJNIEnv();
     AutoJObject obj = m_javaGlue->object(env);
-    // if this is called after DESTROY is handled in WebViewCore.java, mNativeClass
-    // will be null. Do nothing.
+    // if it is called during DESTROY is handled, the real object of WebViewCore
+    // can be gone. Check before using it.
     if (env && obj.get()) {
         env->CallVoidMethod(obj.get(), m_javaGlue->m_needTouchEvents, need);
         checkException(env);