Remove most native WebContents references from Java

content/public/android/java/src/org/chromium/content/browser/webcontents/WebContentsImpl.java

Index: content/public/android/java/src/org/chromium/content/browser/webcontents/WebContentsImpl.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/webcontents/WebContentsImpl.java b/content/public/android/java/src/org/chromium/content/browser/webcontents/WebContentsImpl.java
index ed916e4dbb33945f3683201ffde66724cd3a78e9..15ec7e2de68746c70f193a7ed33b49c870acb655 100644
--- a/content/public/android/java/src/org/chromium/content/browser/webcontents/WebContentsImpl.java
+++ b/content/public/android/java/src/org/chromium/content/browser/webcontents/WebContentsImpl.java
@@ -38,7 +38,7 @@ import org.chromium.content_public.browser.WebContents;
     }
 
     @CalledByNative
-    private void destroy() {
+    private void clearNativePtr() {
         mNativeWebContentsAndroid = 0;
         mNavigationController = null;
     }
@@ -49,6 +49,11 @@ import org.chromium.content_public.browser.WebContents;
     }
 
     @Override
+    public void destroy() {
+        if (mNativeWebContentsAndroid != 0) nativeDestroyWebContents(mNativeWebContentsAndroid);
+    }
+
+    @Override
     public NavigationController getNavigationController() {
         return mNavigationController;
     }
@@ -292,6 +297,9 @@ import org.chromium.content_public.browser.WebContents;
         callback.handleJavaScriptResult(jsonResult);
     }
 
+    // This is static to avoid exposing a public destroy method on the native side of this class.
+    private static native void nativeDestroyWebContents(long webContentsAndroidPtr);
+
     private native String nativeGetTitle(long nativeWebContentsAndroid);
     private native String nativeGetVisibleURL(long nativeWebContentsAndroid);
     private native boolean nativeIsLoading(long nativeWebContentsAndroid);